Radionuclide techniques for localizing inflammatory processes had relied heavily upon 67Ga-citrate until McAfee and Thakur described the technique for the radiolabeling of leukocytes with 111In-oxine. Since their initial description in 1976 there has been continued development of the radiopharmaceutical, as well as clinical efficacy. At present 111In-labeled leukocytes continue to be handled as an investigational new drug but this has not greatly limited its clinical availability. Indium-111 leukocytes are the agent of choice for evaluation of patients with fever of unknown origin, osteomyelitis, and prosthetic graft infections; and preliminary data shows great promise in the area of detecting reocurrence of inflammatory bowel disease. This article attempts to review currently accepted uses of 111In leukocytes as well as potential areas of application.