The records of 83 patients with intra-abdominal abscesses treated between 1986 and 1990 were reviewed to determine if there were significant differences in the outcome of patients treated by surgical drainage (n = 41) or percutaneous drainage (n = 42). The two groups were matched for age, abscess location, and etiology. Parametric statistical evaluations included the Student's t test as well as analysis of variance; nonparametric statistics used were chi-square and Wilcoxon rank sums. No significant difference was found in mortality (surgical 14% versus percutaneous 12%) or morbidity (surgical 26% versus percutaneous 29%). The duration of hospital stay was similar. Although there was no significant difference between the two groups in severity of illness as measured by APACHE II scores, these scores were significant in determining prognosis. APACHE II scores were significantly higher in non-survivors of both groups (23 versus 13) and also higher in those developing complications. A subgroup of patients with diverticular abscess was identified in whom percutaneous drainage enabled later resection with primary anastomosis without complication. This study indicates that percutaneous drainage of an intra-abdominal abscess is as efficacious as surgical drainage and that APACHE II scores are prognostic of both potential mortality and morbidity.