To examine whether agreement between self-reported and accelerometer-measured physical activity varies by BMI category in a low-income black sample.Participants completed a questionnaire and wore an accelerometer for 4-6 days. Using one- and 10-minute bouts, accelerometers measured light, moderate, and vigorous physical activity time.Correlations varied by obesity (nonobese: one-minute r=0.41; 10-minute r=0.47; obese: one-minute r=0.21; 10-minute r=0 .14). Agreement was highest among nonobese persons (one-minute kappa = 0.48, 10-minute kappa = 0.023; obese: one-minute kappa = -0.024, 10- minute kappa = -0.020).We found compromised questionnaire performance among obese participants.