Drug-induced kidney injury is a potential complication of a number of medicaments. The wide-spread use of estrogens in the form of oral contraceptives and in the form of hormonal replacement therapy, has necessitated extensive studies on the biochemical alterations. The following effects of estrogens on kidney are discussed in greater detail with special regard to enzyme induction. The aim of the study was to evaluate the influence of long-term activity estrogens on kidney lysosomal enzymes like cathepsin B, D and L. Female rats were divided randomly into eight experimental groups. Oestradiolum benzoicum was used for the purpose of this study. Estrogens were given i.m. one time per week for 8 weeks in different doses, respectively: E1--0.00075 g/kg b.w., one time per week; E1.1--0.00075 g/kg b.w. every three days; E2--0.0015 g/kg b.w.. one time per week. E2.1--0.0015 g/kg b.w.. every three days; E3--0.03 g/kg b.w.. one time per week; E3.1--0.003 g/kg b.w.. every three days; KO--untreated animals; K1--treated control, rats received oleum pro injection at the dose of 1.2 ml/100 g b.w. The activity of free and bound fractions of lysosomal enzymes, such as cathepsin B, D and L were assayed in kidney homogenates using spectrophotometric methods. Differences between various experimental groups were tested with ANOVA test. The activity of cathepsin B, D and L fractions showed significant changes compared to control groups. The observed changes were not characteristic in all the studied groups. The most important changes referred to the activity of cathepsin B and D. Differences were noted between the enzymes activity in animals treated with the smallest dose of estrogen and that in control groups. It was smaller in group E1 than in groups K0 and K1. The activity of cathepsin B was higher in group E1 than in control groups. There was no correlation between the dose of injected estrogens and the observed lysosomal activity changes. The changes in lysosomal activity were uncharacteristic.