Self-reported weights and heights of 82 adults were compared with measured weights and heights 1 to 3 years after participation in community weight loss programs. The mean self-reported weight was 2.3 +/- 1.9 kg lower than measured weight (P < .05). Differences in underreporting were not significant for gender or age group. Heavier individuals misreported their weight to a greater extent (P < .05) than lighter persons, and individuals who had not recently weighed themselves underreported their weight to a greater extent than those who had weighed recently (P < .05). On the average, height was overreported by a mean of 1.8 +/- 2.7 cm. Overreporting increased with increasing height, and men overestimated their height to a greater extent than women (P < .05). Younger subjects reported their height more accurately than those older than 60 years. Results of our study are similar to those of previous investigations that examined self-reporting bias in subjects enrolled in weight loss programs. The mean discrepancy in body weight, however, was greater than that reported in samples drawn from the general population. Our findings indicate that self-reported weight and height values in overweight populations should be interpreted with caution.