Two hundred and twenty-two patients presented with clinical suspicion of an abdominal or pelvic abscess. Abscesses tend to locate in the perihepatic spaces or the pelvis, and these areas can easily be examined by ultrasound, using the liver or the urinary bladder as acoustic windows. Thirty-eight of 42 abdominal abscesses, and 32 of 33 pelvic abscesses were correctly diagnosed and located by ultrasound, giving a sensitivity of 93.3%. Of the 145 patients without abscesses, 143 were correctly excluded, giving a specificity of 98.6%. Thirty of these patients also underwent gallium 67 examination. This detected all 7 true negatives and all 10 abscesses, 1 of which was missed by ultrasound. Of the remaining 13 patients with positive gallium results, 10 had nonspecific uptake in diffuse inflammatory conditions, and 3 were false positives with uptake in bowel or in a surgical wound. In those patients with nonspecific gallium uptake, ultrasound was valuable in documenting the absence of an abscess cavity. Conversely, gallium detected a left subphrenic abscess missed by ultrasound. For reasons of economy, speed, and high sensitivity, we believe that ultrasound should be the initial screening procedure for patients with clinical suspicion of abdominal or pelvic abscess. Gallium should be reserved for patients with equivocal ultrasound results of those with septic foci not revealed by ultrasound.