Parabens are alkyl esters of p-hydroxybenzoic acid widely used as preservatives in foodstuffs, cosmetics toiletries and pharmaceuticals. These compounds are known to exert a weak estrogenic activity in estrogen receptor assays in vitro. In addition butyl and propyl parabens show uterotrophic activity in vivo. It was previously shown that exposure of post-weaning rats and mice to butyl or propyl parabens adversely affects the secretion of testosterone and the function of the male reproductive system. In the present study, it is shown that methyl and ethyl parabens do not adversely affect the secretion of sex hormones or the male reproductive function. Methyl and ethyl parabens were administered to 25-27-day-old rats assigned to five groups of eight animals each, at doses of 0.1% and 1.0% each in the rat's diet. At the end of 8 weeks, the rats were sacrificed by decapitation and the weights of the testes, epididymides, prostates, seminal vesicles and preputial glands were determined. There were no treatment-related effects of either compound on the organ weights in any of the study groups. Neither compound exhibited anti-spermatogenic effects nor elicited changes in levels of testosterone, LH and FSH at a dose level of about 1000 mg/kg of body weight per day.