The incidence of 5 cases of bilateral renal-cell carcinomas and one case of possible bilateral angiomyoliposarcomas over a period of 16 years suggests than these entities may be more frequent that previously thought. One patient successfully underwent surgery via the "workbench" technique, in which the tumor was dissected from one kidney which was then reinserted as an autograft. It is suggested that renal angiography should always be performed bilaterally when attempting to diagnose or exclude renal masses.