The technique, results, and complications of 109 consecutive sonographically guided therapeutic paracenteses performed on 43 patients with malignant ascites are summarized. A 5.5-French Sacks One-Step Catheter was used in all cases but five in which tissue resistance prohibited passage of the catheter through the abdominal wall. The procedure was performed on an inpatient basis 70 times and in an outpatient setting 39 times. Colonic, ovarian, and breast carcinomas accounted for over 50% of the tumors resulting in malignant fluid collections. Three complications (hypotension, 2.6%) were directly related to the procedure; two of them were fatal (1.6%). The amount of ascitic fluid drained within the first 24 hr averaged 3.5 l at rates of 100-150 ml/sec. Ninety-five procedures (87%, in 39 patients) resulted in improvement of symptoms after drainage as manifested by decreased pain from abdominal distention, alleviation of nausea, improved appetite, or decreased dyspnea. The duration of symptomatic relief ranged from 4 days to 45 days (mean, 10.4 days). Sonographically guided paracentesis is an effective procedure that can be performed for short-term relief of symptoms caused by malignant ascites.