The activities of eight lysosomal enzymes were measured by spectrophotometric/spectrofluorimetric techniques in the blood sera of 19-24 apparently healthy women using an oral contraceptive (progestin and oestradiol synthetic derivative, desogestrel+ethinyloestradiol) in comparison with 15-16 non-pregnant women not using contraceptives (controls), in a randomised, double-blind, controlled study. beta-Glucuronidase and arylesterase showed statistically increased activities (P < or = 0.05) in the experimental group in comparison to the controls. No significant differences were found for the remaining enzymes assayed (beta-N-acetylhexosaminidase, alpha-L-fucosidase, alpha-mannosidase, beta-galactosidase, alpha-galactosidase and acid phosphatase). Similar results were obtained when the contraceptive formed by the combination of levonorgestrel and ethinyloestradiol was used by an experimental group of eight healthy women. These results suggest that the significant increases in the above-mentioned activities might be the physiological response of the organism (through catabolic processes catalysed by lysosomal enzymes) to the administration of exogenous synthetic compounds, such as the oral contraceptives used.