Recent epidemiologic evidence indicates an association between fat distribution and many diseases. To assess the validity of circumference measurements obtained by self-report, the authors analyzed data from 123 men aged 40-75 years and 140 women aged 41-65 years, drawn from two large ongoing prospective studies. On mailed questionnaires, subjects were asked to measure and record their weight and waist and hip circumferences. These data were compared with standardized measurements taken approximately six months apart by technicians who visited participants at their homes. Crude Pearson correlations between self-reported waist circumferences and the average of two technician-measured waist circumferences were 0.95 for men and 0.89 for women. Similar correlations for hip measurements were 0.88 for men and 0.84 for women, and for waist-to-hip ratios, 0.69 for men and 0.70 for women. After adjusting for age and body mass index (kg/m2), correlations for waist-to-hip ratios were 0.55 for men and 0.58 for women. Correlations became stronger after correcting for random within-person variability from daily or seasonal fluctuations. Self-reported and measured weights were highly correlated: 0.97 for men and 0.97 for women. Self-reported waist, hip, and weight measurements appear reasonably valid. The moderate degree of measurement error for the ratio of self-reported waist and hip circumferences, however, implies that previously reported associations based on self-report of these measures may have been appreciably underestimated.