Findings in increasing numbers of clinical and epidemiological studies suggest gender-related differences to exist in the clinical efficacy and adverse effects of drug treatment. Pharmacokinetic studies have shown that the rate of systemic clearance adjusted for body mass may be significantly higher, or lower, in women than in men, which may partly be explained by sex differences in drug metabolism. However, sex differences have also been demonstrated in drug response at the receptor level, though few studies have been focused on this aspect. Many but not all, such gender-related differences can be explained by the effects of sex hormones. There is a need of more systematic analysis of gender-related differences in pharmacodynamics.