The records of 122 patients with non-Hodgkin's lymphoma were reviewed, and the findings of the gallium scan analyzed. The scans of 93 patients were reread without knowledge of the previous readings. Two nuclear medicine physicians agreed with the original readings in 70 per cent of the cases and with each other in 89 per cent of the cases. When the data are analyzed case by case, 52 per cent true positive, 13 per cent false positive and 34 per cent false negative scans were found with only 17 per cent of the scans locating disease not found by routine physical examination and roentgenograms. Looking at individual sites of disease, the gallium scan yields an over-all detection of diseased sites of 18.5 per cent, with 72 per cent of all sites being correctly classified as positive or negative. The diffuse histiocytic, mixed and undifferentiated histologies were detected more accurately than all others, with mediastinal and extranodal sites being identified more frequently than any nodal site. The gallium scan revealed a site of disease which advanced the clinical stage in only one of 122 patients (upstaged). Only one of 122 patients was upstaged as a result of gallium scanning. These data suggest that gallium scanning may not be cost effective in the routine staging of patients with non-Hodgkin's lymphoma.