OBJECTIVE Two routine lung SPECT studies showed what appeared to be uptake within the gallbladder. This finding was confirmed on coronal views and three-dimensional reconstruction. There was no contamination or problem with the radiopharmaceutical quality control. The patients had not had any prior nuclear procedures. Gallbladder visualization on routine lung imaging has not been previously observed. The purpose of this study was to ascertain the incidence of gallbladder uptake and to determine a possible mechanism. METHODS Fifty-four patients referred for routine lung perfusion imaging were examined. At the end of the lung imaging, an anterior and/or right lateral 3-5 minute view of the abdomen was obtained. Patients too ill for additional imaging or those with prior cholecystectomies were excluded. RESULTS Nineteen of the 54 patients showed activity within the gallbladder. Activity within the gut, kidneys, and urinary bladder also were observed. CONCLUSIONS Gallbladder activity after Tc-99m macroaggregated albumin injection for lung perfusion studies, is a fairly common finding.