The 13th case of malignant interstitial cell tumor of the testicle is reported, and review of the literature made. Six cases of malignant interstitial cell tumor were associated with hydroceles. Absence of urinary chorionic gonadotropin levels does not indicate a more favorable prognosis. The average age at discovery of malignant interstitial cell tumor is 60 years. Retroperitoneal lymph nodes, lung, liver, and bones are the most frequent sites of metastatic involvement. The best treatment appears to be radical orchiectomy and surgical resection of metastases. Chemotherapy may offer remission when surgical resection of metastases is not possible.