Portacaval anastomosis in male is known to induce testicular atrophy. The effect of liver revascularization by the right renal artery on the testes of portacaval shunted rats was examined. After shunting, there was a 75% decrease in testis weight compared to the control value and spermatogenesis was blocked in steps 8–9 of spermiogenesis. The in vitro binding of [125I]hCG was only 10% of the control value on a per testis basis and labelled areas in the interstitium of frozen sections subjected to topical autoradiography with [125I]hCG were also strikingly reduced. These parameters were maintained to normality in revascularized shunted rats which displayed also normal copulatory and fertilizing abilities. It is suggested that an adequate blood supply to the liver, as provided by arterialization, can preserve testicular integrity in shunted rats, even though the blood is arterial instead of porta