The army itch was a chronic, severely pruritic dermatosis which first appeared among soldiers and some civilians early in the American Civil War (1861-1865). As the war progressed, so did army itch, becoming epidemic in the Potomac Valley of Maryland in 1862 and in Virginia in 1864. Immediately after the war, civilian cases traceable to contact with returning soldiers focused attention on the disorder, but the postwar outbreaks were short-lived and the army itch disappeared by the end of 1867. The origin of army itch eluded medical observers of the time, though many considered epidemic scabies to be the cause. Many cases of army itch were successfully treated with scabicides, but the disease had a well-deserved reputation for intractability. After a review of the chronology of army itch and excerpts from the writings of physicians who saw and treated the disease, it is possible to conclude that army itch was epidemic scabies, though the clinical picture was frequently confounded by coexisting pediculosis, prurigo, and other pruritic dermatoses.