Scintigraphy with 99mTc-labeled anti-granulocyte antibodies (AGAb) was performed in 50 patients with suspected appendicitis. Sequential and static imaging as well as SPECT of the pelvis and abdomen was performed 2 h p.i. In all patients the diagnosis was confirmed either histologically or by long-term follow-up. 13 patients had histologically proven acute appendicitis. In 11 patients the appendix scan had been positive and in 2 patients the scan had shown no significant tracer uptake in the right lower abdomen. The remaining 37 patients turned out not to have acute appendicitis. 29 out of these patients had negative and 3 had positive scan findings. In 5 patients the scan was equivocal. Out of these patients 2 had pathologic findings on the left side of the abdomen which turned out to be acute diverticulitis in one patient and acute peritonitis in the other. The remaining 3 patients with unclear scintigraphic findings had no acute appendicitis. Scintigraphy with AGAb is fast and easy to perform and thus superior to cell labeling methods for diagnosing acute appendicitis. Sensitivity for the diagnosis of acute appendicitis was 85% with a specificity of 91%. Chronic or scarred non-granulocytic appendicitis--in which there is often no definite indication for surgery--was negative in our study except for two cases.