Subcutaneous injection of chloroform to male mice of various strains results in renal tubular necrosis. In contrast, the females do not develop any renal lesions. The purpose of this work was to determine whether in this respect testosterone is noxious and the female hormones protective. Ovariectomized females failed to develop renal tubular necrosis analogically to the intact ones. This means that a lack of female hormones does not endanger these animals. However, chloroform-induced renal tubular necrosis was found in a considerable proportion of ovariectomized mice, if treated with testosterone. Testectomized males appeared to be free of any renal lesions after injection of chloroform. The presence of testosterone in the body seems to be a prerequisite for chloroform-induced renal tubular necrosis.