Adrenogenital syndrome (AGS) is the result of inborn enzymatic defects in the synthesis of steroid hormones. The production of cortisol is deficient and that of adrenocorticotropic hormone is increased. Sometimes male patients have clinically detectable testicular lesions, known as testicular tumors of AGS (TTAGS). From 1985 to 1991, scrotal ultrasonography (US) was performed in 30 consecutive pubertal and postpubertal patients with AGS to investigate the prevalence and US characteristics of TTAGS. Eight of 30 patients had a testicular lesion (27%); six of the eight lesions were clinically undetected. The mean diameter of the lesions was 16.44 mm (range, 2-28 mm). The lesions were hypoechoic in all cases, with well-defined margins in six cases. The nodules were multifocal in all patients and bilateral in six (75%). If testicular lesions are present in a patient with AGS, TTAGS are likely, and frequent US monitoring is adequate for diagnostic evaluation.