The Army Combat Uniform (ACU) is the current combat uniform worn by the United States Army. It is the successor to the Battle Dress Uniform (BDU) and Desert Camouflage Uniform (DCU) worn during the 1980s and 1990s. It features a number of design changes, as well as a different camouflage pattern from its predecessor. The ACU and its component materials are manufactured by the existing industrial infrastructure which produced the now-obsolete BDU.
The ACU uses a new military camouflage pattern called the Universal Camouflage Pattern (UCP), which blends green, tan, and gray to work effectively in desert, woodland, and urban environments. Similar to the United States Marine Corps MARPAT and Canadian CADPAT camouflage schemes that preceded it, the pattern design is based on research into Dual Texture (Dual-Tex) Camouflage conducted in the 1970s.
The color scheme of the Army Combat Uniform is composed of a slate gray, desert sand and foliage green pixel pattern, which becomes darker or lighter depending on exposure to sunlight. The shade black was omitted from the uniform since it does not exist in nature.  Pure black, when viewed through night vision goggles, appears excessively dark and creates an undesirable high-contrast image.
Soldiers have reported that the nylon cotton fabric does breathe better than the cotton Desert Camouflage Uniform (DCUs) and results in a cooler uniform in high temperature climates.
The uniform features hook-and-loop fasteners on the pockets.
The cost to each soldier is $76 per uniform, compared to $58 for a BDU, but clothing allowances in soldiers' pay have been adjusted to compensate for the increased cost. Insignia and tags, such as name and branch tapes, are extra purchases. Uniforms purchased from commercial websites and surplus stores that sell to the general public do not include the IR squares, which are restricted to military personnel because of their sensitive nature.
The ACU jacket uses hook-and-loop-backed attachments to secure items such as name tapes, rank insignia, and shoulder patches and tabs, as well as recognition devices such as the American flag patch and the infrared (IR) tab.
Near Infrared (NIR) Signature Management Technology is incorporated to minimize the infrared silhouette. Permanent IR IFF squares are sewn to each shoulder to help identify friendly personnel when night vision devices are used, and are protected by Velcro tabs in garrison or when not in use.
Three U.S. flag insignia are authorized for wear with the ACU: full-color, full-color IR, and subdued IR. The U.S. flag insignia (full-color or subdued) is worn on the right shoulder pocket flap of the ACU coat. The subdued version is only worn as directed under tactical or field conditions. On the right shoulder of the ACU, the U.S. flag is depicted with the union (stars) to the viewer's right, instead of the usual left (flag's own right); this is to give the impression of the flag moving forward with the wearer. Subdued shoulder sleeve insignia are always worn.
The jacket's Mandarin collar is worn up in combat to fit with the Improved Outer Tactical Vest (IOTV) body armor, and worn in the down position otherwise. The front closure is zippered and reinforced with velcro, designed for use with OTV. The tilted chest pockets, cuffs, and elbow pad insert pockets also utilize hook-and-loop closure. There is a three slot pen pocket on the left arm of the jacket, and blouse bellows for increased mobility.
Only pin-on skills badges are authorized for wear on the ACU, and no more than 5 may be worn at any one time. Skills tabs, such as the President's Hundred Tab, Special Forces, Ranger, and Sapper are worn on the left sleeve pocket flap, and are subject to a 3 tab only rule. A tab that is an integral part of a unit patch, such as the "Mountain" or "Airborne" tab, is not counted against the rule. The U.S. Army Chaplain insignia is the only authorized branch insignia to be worn on the ACU. It is centered 1/8 inch above the right name tape. The insignia may be the metal pin-on variety or the black embroidered insignia on digitized fabric with hook and loop (Velcro) fasteners.
Current regulations require the jacket to not extend below the top of the cargo pocket and not be higher than the bottom of the side pocket. Sleeves are to be worn down at all times, in contrast with the earlier Army BDU policy which authorized sleeve-folding for the summer uniform.
The M65 Jacket comes in the ACU pattern but this time with no shoulder epaulettes, unlike the previous M81 BDU field jacket. All four front pockets are kept, velcro patches were added to the sleeves and front with a small tab in the centre for rank slides much like the British Combat 95's. The jacket has an optional foliage green liner. It is going to be replaced by a jacket from the ECWCS line of clothing.
The ACU trouser is worn with a two-inch nylon web belt, and features Velcro pouches for knee pad inserts, two forward-tilted thigh storage pockets with elastic drawstring and Velcro for closure during movement, and two calf storage pockets one on each pant leg with a Velcro closure. In addition, the pants legs can be bloused and must not extend past the third eyelet of the boots as per AR 670-1. Army Combat Pants, which are identical to the ACU trousers except for their flame resistant materials, are being issued for use in Iraq and Afghanistan.
In the field, the ACU is worn with the MICH TC-2000 Combat Helmet, a patrol cap, or a boonie hat as appropriate. In garrison, the maroon paratrooper, tan United States Army Rangers, green United States Army Special Forces or black conventional unit beret or patrol cap is worn. The patrol cap is a straight-sided, flat-topped soft cap, with a double thick bill and internal pocket. The foliage green or black micro fleece cap or a black knit cap is authorized in cold climates. ref name="Fleece Cap">Fleece/Knit Cap Authorization for the ACU</ref> (This is not included in the attached ALARACT. It refers to wear with the IPFU only).< The name tape is worn on the back of the patrol cap. Sew-on rank is recommended but pin-on rank is authorized on the ACU Patrol Cap and ACU Boonie Hat. The MICH (Modular Integrated Communications Helmet) Camouflage cover rank must be sewn on if worn but is often not used as the Night Vision Device mount would obstruct it.
The ACU is worn with a moisture-wicking sand colored T-shirt. A Foliage Green T-shirt, which is 100% cotton, has been authorized for wear by select soldiers. Also under some training environments or special occasions custom black and tan unit shirts are worn.
The ACU is worn with tan Army Combat Boots and moisture wicking socks. Commercial versions of this boot are authorized without limitation, complying with the following regulations — be at least 8 inches in height, be made of tan rough side out cattle hide leather with a plain toe and tan rubber outsoles, and be without zippers, metal cleats, or side tabs.
Although common practice (though not required by regulation) with the BDUs, ACUs are not to be starched. As per the ALARACT message in effect until a new revision of AR 670-1 is released, "Soldiers will not starch the Army Combat Uniform under any circumstances. The use of starch, sizing, and any process that involves dry-cleaning or steam press will adversely affect the treatments and durability of the uniform and is not authorized."
Starching the uniform has been shown to cause discoloration. It enhances the IR signature, making the uniform inappropriately bright under night vision viewing.
Personnel have been instructed that the uniform must be washed with a mild detergent that does not contain "optical brighteners." Detergents with optical brighteners may cause discoloration of the uniform, which would nullify the purpose of the very specific camouflage design and result in possible unwanted detection of personnel using the uniforms in combat. Some detergents have phosphorescent properties which enhance an enemy's ability to see the soldier when viewed with Night Vision Devices.
Soldiers have expressed concern about the velcro on the ACU. Dirt and mud can clog the hooks and loops or they can wear out with use, requiring the use of cleaning brushes for clearing the velcro as part of daily maintenance. Zippers have also been a topic of concern. Soldiers also express concern because the zippers (as with any zipper) can bind up, and render the uniform uncomfortable to wear, especially with Body Armor. According to the Program Executive Office Soldier "Commercial Velcro will be sold in clothing sales for the repair/replacement of Velcro. Additionally soldiers have been using the small weapons cleaning brush to clean out any sand and dirt from the pile and it has been working very well." 
The process of replacing the Army's Woodland (in use since 1981) and Three Color Desert pattern BDU with the ACU was to begin in April 2005; however, the process began two months earlier through the Rapid Fielding Initiative. Soldiers from the 48th Infantry Brigade Combat Team were the first Army unit, active or reserve, to receive the ACU, subsequently deploying the entire Brigade into OIF combat in May 2005. Initial reception of the ACU was mixed, with complaints of insufficient durability and excessive maintenance. The use of multiple camouflage patterns within an organization is now seldom seen, as the ACU has been widely fielded.