When testicular tumors were ultrasonographically examined via real-time scanning in 51 patients during the last 10 years, the tumors were all accurately diagnosed. On histological classification, the tumors were found to show one histological type in 27 patients (seminoma in 20, embryonal carcinoma in 4, yolk sac tumor in 2 and teratoma in 1) and more than one histological types in 14 patients (embryonal carcinoma + teratoma in 7, choriocarcinoma + other types in 2 and other combinations in 5,) and to be secondary tumors in 10 patients (lymphatic leukemia in 6 and malignant lymphoma in 4). Although masses tomographically showed a solid pattern in 39 of the 51 patients (76%), the echogenicity of these masses was all lower than that seen in the normal testicular tissue. Small masses, measuring less than 5 cm in maximum diameter, especially showed homogenous internal echos as often as 50%; most of these masses with homogenous internal echos were anechoic. According to histological types, all the yolk sac and secondary tumors and 90% of seminomas showed this echo pattern. A mixed echo pattern was seen in 12 patients (34%). According to histological types, although the teratoma showed a mixed pattern, 50% of embryonal carcinomas and tumors of more than one histological types had this pattern. Among testicular tumors found in the 51 patients, the number of tumors being able to be compared as to their histopathological types with their tomographic findings was unexpectedly small. Therefore, it seems to be important to make preoperative diagnosis based on the age of the onset of testicular tumor in combination with tumor marker and tomographic findings.