Purpose: To evaluate the criterion validity of the 7-Day Physical Activity Recall (7D-PAR) and factors associated with reporting error, in a sample of moderately overweight, young adult men and women. Methods: Average total daily energy expenditure (TDEE) and physical activity energy expenditure (PAEE) from the 7D-PAR were compared with the same parameters assessed by doubly labeled water in 17 men, age = 23.9 ± 3.8 yr, and 29 women, age = 23.3 ± 4.6 yr, who volunteered to participate in a 16-month supervised aerobic exercise trial. PAEE was estimated from the 7D-PAR and from DLW [0.9 * TDEE - resting metabolic rate (RMR) (indirect calorimetry)]. In addition, peak oxygen uptake and percent body fat were obtained Results: No significant differences in TDEE (kJ.d-1) were noted between the 7D-PAR (11,825 ± 1,779) and DLW (11,922 ± 2,516) for the complete sample (N = 46) or for men (7D-PAR = 13,198 ± 1,638, DLW = 13,885 ± 2,754) or women (7D-PAR = 11,018 ± 1,323, DLW = 10,771 ± 11457. The mean PAEE from the 7D-PAR was not different from DLW in the total sample (7D-PAR = 3286 ± 502, DLW = 3508 ± 1863) as well as in men (7D-PAR = 3650 ± 490, DLW = 3989 ± 2461) and women (3073 ± 377, DLW = 3223 ± 1360). In a regression model, PAEE, peak oxygen uptake, gender and percent fat accounted for 86% of the reporting error in total daily energy expenditure when using the 7D-PAR. Conclusion: The 7D-PAR provided a reasonable estimate of both the mean TDEE and PAEE in this sample; however, estimates of energy expenditure on an individual basis using the PAR were subject to considerable error.