Scrotal imaging with technetium-99m sodium pertechnetate consists of a radionuclide angiogram and static scrotal scans. Utilization of this study in patients presenting with an acute scrotum can dramatically reduce the number of surgical explorations for acute epididymitis. It can also aid in other aspects of differential diagnosis in patients presenting with either an acutely enlarged and/or painful scrotum or a scrotal mass. Ambiguities in previous descriptions of perfusion through the spermatic and extraspermatic cord vessels are described and distinguished from scrotal perfusion. The clinical and scintigraphic spectrum of testicular torsion, including spontaneous detorsion, early acute testicular torsion, midphase testicular torsion, and late phase or "missed testicular torsion", is discussed and illustrated. The variety of patterns seen in acute epididymitis, including lateral and medial epididymal location, and focal epididymitis are described, as is the appearance of hydrocele as both a primary and secondary entity. The relationship of scrotal imaging to the overall clinical presentation and evaluation of these patients is emphasized in testicular torsion, torsion of the testicular appendages, epididymitis, abscess, trauma, tumor, spermatocele, and varicocele. The techniques, clinical utility, and relationship to radionuclide imaging of Doppler ultrasound and gray scale ultrasound scanning are reviewed. Doppler ultrasound results in many false negative studies in testicular torsion. Gray scale ultrasound is useful in clarifying the nature of scrotal masses.