Technical Abstract: Physical activity energy expenditure is an important determinant of health and epidemiologists have used various methods such as physical activity and energy intake recalls and records to estimate energy cost. However, most epidemiological studies have not validated these methods against the doubly labeled water (DLW) technique for determining energy expenditure (EE). The objective of this study is to compare EE estimated by indirect methods using four physical activity questionnaires with EE obtained from DLW in free-living postmenopausal women. We determined EE using the DLW method and EE from the Harvard Alumni questionnaire, Five City Project questionnaire, the Cross-Cultural Activity Participation Study (CAPS) Four Week Activity Recall and the CAPS Typical Week Activity Survey in 65 healthy postmenopausal women. Compared to DLW, the Harvard Alumni questionnaire, the Five City Project questionnaire and the CAPS Four Week Activity Recall overestimated (P<0.05) daily energy expenditure (EE) by 70%, 30%, and 68% respectively. The CAPS Typical Week Activity Recall underestimated (P<0.05) EE by 16% compared to the DLW method. Obese and overweight women were found to significantly overestimate EE compared normal weight women on the Harvard Alumni questionnaire and the Five City Project questionnaire. In this intervention, Postmenopausal women were found to overestimate EE estimates using three of the four questionnaire methods (Harvard Alumni questionnaire, Five City Project questionnaire, and the CAPS Four Week Activity Recall) and to underestimate EE on the CAPS Typical Week Activity Recall. Obese women may overestimate daily EE the most.