Comparison of self-reported and measured weights in a working population of 2046 men and 2393 women revealed systematic underreporting of 1.3% in men and 1.7% in women. Underreporting was significantly related to weight, height, and current participation in a weight reduction program in both men and women. In men only, it was also related to age, education, history of weight-control attempts, and history of weight-related health conditions. Overall, however, these predictor variables accounted for a small fraction of the variance in underreporting and the correlation between measured and self-reported weight was very high (rs = .99). It is concluded that self-reported body weight is an excellent approximation of actual weight across a broad range of population subgroups.