OBJECTIVE To determine if the sonographic appearance of solid extratesticular masses enables distinction of benign from malignant disease. METHODS Sonograms of 19 patients with palpable testicular masses who underwent biopsy were reviewed retrospectively. Appearances of masses on sonograms were correlated with pathologic diagnoses. RESULTS All masses were well defined and ranged in size from 5.7 to 66.7 mm (mean, 21 mm). On the sonograms, five masses were within the epididymis, and six were distinct from it; seven cases were indeterminate. The epididymis was surgically absent in the remaining patient. Sonographic echogenicity ranged from hypoechoic to hyperechoic relative to that of the testis. At pathologic evaluation, there were 16 (84%) benign and three (16%) malignant lesions. Benign lesions consisted of six adenomatoid tumors, two lipomas, two epidermoid inclusion cysts, two cases of sarcoidosis, and one case each of sperm granuloma, spermatic cord leiomyoma, benign inflammatory nodule, and fibroma. The malignant lesions consisted of scrotal wall liposarcoma, epididymal leiomyosarcoma, and recurrent spindle cell malignancy of the spermatic cord. No sonographic features of masses were useful for distinguishing benign from malignant lesions. CONCLUSIONS The frequency of malignancy (16%) contrasts with prior reports that suggest a very low rate of malignancy among these masses. Sonography is useful for identifying the extratesticular location of a mass but not for distinguishing the nature of the lesion.