To improve diagnostic capabilities, an ultrasound unit was installed at a major hospital in Wad Medani, Sudan. During the implementation period (October 1986 to March 1987) of ultrasound service, 863 patients were examined cooperatively by Sudanese and German physicians. The service covered internal medicine (47.5%), obstetrics and gynecology (31.6%), surgery (12.5%), and pediatrics (8.4%). Pathologic findings were seen in 75% of the patients. In obstetrics, the rate of pathologic findings was 40%. Five hundred eighty-three pathologic findings were detected in organ systems that constituted the primary indication for ultrasonography (of a total of 1,009 indications). The clinical benefit of ultrasonography was evaluated in 289 randomly selected patients in a standardized questionnaire completed by the attending physicians. The final clinical diagnosis was established or substantially revised in 21.5% of the patients, based on the ultrasonographic report. The previously reported diagnosis was supported in 69.5% of the patients. Medical management was directly influenced in 26% of the patients. We conclude that the clinical benefit of ultrasonography at a district hospital in the tropics is substantial, providing cost-effective, immediate therapeutic benefits in 25% of the patients examined. The technique thereby contributes to better and more rational patient management in institutions with limited resources.