Ke 6 is a 17beta-hydroxysteroid dehydrogenase that is expressed in several somatic tissues as well as the female reproductive tissues. We previously correlated a dramatic reduction in the expression of the Ke 6 gene with the development of recessive polycystic kidney disease, in three murine models, the cpk, jck and pcy mice. We also determined that in one of the murine models, the cpk mouse, the female reproductive organs fail to mature properly and remain arrested at an early stage of development. In this study, we report the expression of the Ke 6 protein in normal male reproductive tissues by immunofluorescent staining. We determined in the cpk mouse that the testes similar to the immature ovaries, is also under-developed and arrested at an early developmental stage. Direct measurement of 17betaHSD activity showed a conspicuous reduction in sex steroid metabolism in the cpk/cpk testes. Our findings suggest that estrogen/androgen metabolism play an important role in the development of the urogenital system.