The influence of two inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase, simvastatin and pravastatin, on the level of urinary 6 beta-hydroxycortisol/17-hydroxycorticosteroids (6 beta-OHC/17-OHCS) ratio was determined in two groups of normolipidemic Caucasian subjects (n = 18 and n = 14, respectively). The 6 beta-OHC/17-OHCS ratio increased significantly after simvastatin administration (20 mg day-1 for 17 days) (P = 0.0125) whereas no modification was observed after pravastatin administration (20 mg day-1 during 17 days). As the level of 6 beta-OHC/17-OHCS ratio is a function of cytochrome P-450 3A activity, these results suggest that in Caucasian subjects, simvastatin but not pravastatin could be a weak inducer of cytochrome P-450 3A. This contrasting effect could be related to the major pharmacological differences existing between these two drugs.