Nonspecific polyclonal immunoglobulin (IgG), prepared from pooled human serum gamma globulin and labeled with 111In has been reported to be equivalent to antigen-specific antibody in the detection of focal infection or inflammation during the first 24 hr after injection. We describe our experience in a Phase II clinical study using 111In-IgG in 15 patients (8 males, 7 females) ranging from 26 to 80 (mean = 50) yr of age with suspected focal infection/inflammation. Pathologic confirmation was obtained in 5/15 cases. A combination of clinical course, laboratory results, and other imaging procedures were used to categorize the other 10 patients. One possible false-negative involved a presumed aspiration pneumonia in a patient with a history of aspiration, bibasilar infiltrates on chest film, and no other identified source of infection. Otherwise, there were 10 confirmed positives, 4 confirmed negatives, and no false-positives. Our findings confirm earlier reports that 111In-IgG may be a superior imaging agent for infection/inflammation with practical advantages over 67Ga-citrate and 111In-labeled leukocytes.