From March 1985 to April 1989, one hundred thirty-one patients were examined using computed tomography (CT) and/or ultrasonography (US) in the evaluation of acute blunt trauma of the abdomen (CT and US in 36 patients, CT in 25 US in 70). Twenty-three out of the 131 cases (17.6%) showed positive findings of abdominal trauma on CT and/or US. Sixteen of the 23 patients with positive findings underwent therapeutic laparotomy, while all of the other 108 patients with negative findings were successfully managed conservatively. This fact suggests that one of the roles of CT and/or US is to pick up patients with negative findings who do not have any laparotomy. Free fluid collection was demonstrated in all of the 23 patients with positive findings in: all 22 on CT (100%), and 13 of 14 on US (92.9%). In all of the 23 patients but one with an injured mesenterium, injured organ was demonstrated by CT and/or US in: 21 of 22 by CT (95.5%), and 11 of 14 by US (78.6%). In one of the 11 patients, not an immediate US but a follow-up on the next day revealed an injured organ. In 6 out of the 12 patients who underwent both plain and contrast enhancement (CE), CT, CE-CT demonstrated the injured organ more clearly than plain CT. US with sector probe was also useful for demonstrating the injured lesion.(ABSTRACT TRUNCATED AT 250 WORDS)