The in vitro and in vivo behaviour of 99Tcm-HMPAO (hexamethylpropyleneamineoxime) (n = 12) and 111In-oxine (n = 11) labelled granulocytes, isolated by density-gradient centrifugation (Metrizamide/plasma gradients), was compared in patients with suspected inflammatory diseases. The in vitro elution of both labels and the viability of the labelled cells (99Tcm, 98.5%; 111In, 96.5%) was comparable but the labelling efficiency was different (99Tcm, 44 +/- 13%; 111In, 72.5 +/- 5.5%). In vivo, the lung (t1/2 max: 7.7 min), liver and spleen perfusion patterns were nearly identical; the image quality for detail in 99Tcm scans was superior to 111In images. The blood disappearance curves of 99Tcm and 111In were comparable. In the small number of patients examined all infections could be diagnosed correctly, without false-positive or false-negative results. Disadvantageous is the renal excretion of 99Tcm complexes (3+% over 20 h) with kidney and bladder activity from the beginning of the study. The biliary excretion in half of the patients (n = 6) with unspecific positive small and large bowel visualization and the late intestinal excretion also render the diagnosis more difficult. The recommended best imaging times for abdominal and retroperitoneal inflammations are 30 min to 2 h after injection. Late scans in septic prosthetic joints have disproportionate long acquisition times. As a potential cell labelling compound, 99Tcm-HMPAO has a promising future in comparison to 111In scans because of the good availability of 99Tcm, the image quality and the lower radiation exposure to the patient when lower activities for the early diagnosis of abdominal inflammatory diseases are reinjected.