Endocrine dysfunction has been associated with renal diseases. The present study was conducted to explore reproductive function in male rats with chronic nephrosis. Experimental chronic nephrosis was induced by the administration of 7.5, 5.0 and 5.0 mg per 100 g body weight of puromycin aminonucleoside on days 0, 21 and 35, respectively. Reproductive function was evaluated on the basis of hormonal concentrations, mass of accessory sex organs and fertility during an 84 day period. Circulating LH, FSH, testosterone and oestradiol concentrations were measured by specific radioimmunoassays, while fertility was estimated by the rate of pregnancy induction. Samples were collected on days 7, 14, 28, 56 and 84. The results showed an important endocrine dysfunction characterized by low concentrations of LH and FSH during the first month, after which concentrations were similar to control values or even increased on days 56 and 84. Testosterone and oestradiol decreased significantly at all time points evaluated. The mass of the testes did not alter. However, the mass of the prostate and seminal vesicle decreased only during the first 2 weeks, and became essentially normal thereafter. The reproductive capacity of nephrotic males was eliminated on day 7, whereas on day 14, 16% of the group was able to mate successfully and subsequently most animals recovered their normal reproductive function. This study demonstrates for the first time that rats with experimental chronic nephrosis develop an important endocrine dysfunction, characterized mainly by persistent reduction in testosterone concentrations, which impairs reproductive capacity only transiently.