Previous studies, including our studies using the alcohol clamp, have shown that alcohol pharmacokinetics differ between women and men. Some of the factors that may contribute to these sex differences in absorption, distribution and metabolism include variation in lean body mass (and total body water), liver size and differences in activity or capacity of alcohol metabolizing enzymes in the stomach and livers of women and men. A fundamental difference between men and women is in the levels of the sex hormones estrogen and testosterone, which can influence several of the above factors. Sex differences in alcohol pharmacokinetics, and estrogen itself, have been postulated as determinants of the increased susceptibility of women to alcohol-related liver disease. An additional area of interest is sex- and age-related differences in sensitivity to the effects of alcohol. The elderly are thought to be more sensitive to alcohol and show greater impairment than younger individuals. However, it is not clear if these changes are due to pharmacokinetic or pharmacodynamic factors.