The effects of active principles os Stevia rebaudiana (Bert.) Bertoni on some endocrine functions in rats were studied after chronic administration (60 days) of a concentrated aqueous extract of the leaves, starting at pre-pubertal age (25-30 days). The following measurements have been carried out: glicemia, T3 and T4serum levels, available T3 binding sites in plasma (T3R), [3H]R1881 binding to prostate cytosol, Zn content in prostate, testis, submaxillary gland and pancreas, and hydric content in testis and prostate. Also, it has been studied the curve of body weight gain and the final weight of testis, prostate, seminal vesicle, submaxillary gland and adrenal. Any significant difference between experimental and control groups were seen, except for the weigth of seminal vesicle which. It was concluded that pharmacological doses of active principles of S.rebaudiana chronically administered to rats did not elicit any fundamental alternation of the endocrine functions studied.