Percentage body fat was determined by skinfold anthropometry and bioelectrical impedance analysis in 60 patients with cirrhosis, 30 of whom had overt fluid retention, and in 60 age- and sex-matched healthy volunteers. In the control population the mean +/- 1SD percentage body fat assessed using bioelectrical impedance analysis, 22.6 +/- 6.5%, and skinfold anthropometry, 22.5 +/- 6.9%, were comparable. However, there was considerable variation in individual values such that measurements made using bioelectrical impedance analysis could be from 9% less to 8% more than the corresponding anthropometric values. In patients with cirrhosis the mean percentage body fat assessed using bioelectrical impedance analysis, 24.4 +/- 8.9%, was significantly greater than the value obtained using skinfold anthropometry, 20.3 +/- 8.4% (p < 0.01) for the whole group and for the subgroup of patients with fluid retention, 24.5 +/- 8.5% cf. 18.4 +/- 7.1% (p < 0.005); estimates of body fat in the subgroup of patients without overt fluid retention were comparable between methods, 24.4 +/- 9.4% cf. 22.1 +/- 9.2%. In the whole patient group individual measurements made using bioelectrical impedance analysis could be from 10% less to 18% more than the corresponding anthropometric values; similar degrees of variation in individual values were observed in the two patient subgroups. Bioelectrical impedance analysis should not be used interchangeably with skinfold anthropometry for assessment of percentage body fat in patients with cirrhosis, irrespective of their state of hydration.