Twenty-seven patients presented with painful acute scrotal swelling. After a clinical impression was established, all patients underwent diagnostic imaging with color Doppler ultrasound (US). Seven patients underwent surgical exploration for testicular torsion diagnosed with color Doppler US (100% operative confirmation), one underwent radical orchiectomy for treatment of seminoma, and one underwent orchidopexy for treatment of a freely mobile testis. Eighteen patients were treated for nonoperable conditions. Diagnoses made with color Doppler US correlated with final clinical diagnoses in all patients. In 10 of 27 patients (38%), the diagnosis was established at color Doppler US. Until now, nuclear scanning has had a paramount role in the evaluation of equivocal cases of acute scrotal disease. Results show that color Doppler US helps accurately correlate anatomy and perfusion in real time and may prove to be the definitive imaging technique for the diagnostic evaluation of acute scrotal pain or swelling.