Tumors of the testis comprise 1% of male neoplasms. Interstitial cell tumors that originate in Leydig's cells account for 1 to 3% of these testicular tumors. A prognosis is difficult to make since these rare neoplasms manifest clinically in variable forms and it is extremely difficult to distinguish the benign from the malignant. Two new cases of this rare tumor type seen at the Department of Urology of the University Hospital of Florence are reported. The literature is reviewed, highlighting the clinical aspects, particularly the symptomatic, histopathologic, and the differential diagnostic features of the less and highly malignant forms. Furthermore, a protocol for selecting the therapeutic modality for this rare neoplasm is described.