The use of gallium scanning for the diagnosis of abdominal abscesses was studied in 59 cases in which the diagnosis was verified by laparotomy or autopsy. In 23 of the cases the patients were subsequently found to have abdominal abscesses and 11 patients had abdominal malignancies. Excluding the latter group, the scan was specific for abscess in 86 per cent of the cases and sensitive for abscess in 67 per cent. Recent abdominal incisions, concurrent intestinal, hepatic, biliary and pancreatic inflammatory conditions, without abscess, seldom caused gallium accumulation. False-negative scans (18 per cent) occurred more frequently than false-positive scans (8 per cent) and were seen in patients with large (often palpable) masses of short evolution and with secondarily infected lesions such as hematomas and pseudocysts. The gallium scan was of little help in the search for abdominal lesions in patients with obscure febrile illnesses without abdominal symptoms or signs.