OBJECTIVE The purpose of this study was to evaluate the clinical efficacy of transvaginal sonographically guided aspiration and drainage of pelvic fluid collections. METHODS Forty patients underwent transvaginal sonographically guided aspiration of a possible pelvic abscess (41 pelvic collections). In patients with clinical findings highly suggestive of infection, both purulent and nonpurulent collections were immediately drained via a catheter. In patients with clinical findings moderately suggestive of infection, nonpurulent collections were completely removed by aspiration and the aspirates were cultured; however, purulent collections were immediately drained via a catheter. RESULTS All collections were successfully accessed by transvaginal sonography. For 27 of the 41 collections, the aspirate was purulent (18 collections) or the patient's clinical findings were highly suggestive of infection (nine collections) and catheter drainage was performed. Seventeen of the 27 collections completely resolved and surgery was not required. Four of the 27 collections were in patients who had surgery for reasons other than persistent infected collection. For six of the 27 collections, catheter treatment was not successful and surgery was required. The overall success rate of catheter drainage was 78%. In the remaining 14 of the 41 collections, the aspirate was serous or serosanguineous, and the patient's clinical findings were moderately suggestive of infection. Cultures of aspirates of seven collections were positive for microorganisms. Eleven collections were successfully treated with antibiotics or no therapy was required (based on culture results); for three, surgery was required. Two complications occurred: one vaginal fistula after catheter drainage and one disruption of vaginal sutures after aspiration. CONCLUSIONS Transvaginal sonographically guided drainage is effective treatment of pelvic abscess, being either completely curative or temporizing in 78% of patients. Catheter treatment was unsuccessful and surgery was necessary in 22% of patients. For nonpurulent collections, catheter drainage is indicated only when clinical findings are highly suggestive of infection.