In order to define the clinical significance and the need for further clinical work-up in patients where abnormalities of the stomach or bowel are found by ultrasound, we performed a prospective study on 100 patients with such findings. Of all patients, 35% were found to have a malignant tumor, 73% had a diagnosis as made by reference methods which was probably (18%) or definitively (55%) related to the US finding. Eighteen percent had definitive false positive findings, in 9% no final diagnosis was obtained. Thus, a positive predictive value of 80% was calculated for the US finding of a mass or a target sign related to bowel or stomach in US. The positive predictive value was lowest for target signs related to the bowel (75%) and highest for bowel conglomerates (100%). Patients with target signs of the stomach, bowel conglomerates, or masses were more likely to have malignant disorders (72%) than those with target signs related to the bowel (16%). We conclude from this study that the ultrasound finding of a target sign or a mass related to stomach or bowel has a high clinical relevance and should in any case worked up by appropriate investigations when clinical consequences are possible.