PURPOSE: To validate and compare four popular physical activity questionnaires for estimating daily energy expenditure (DEE) as compared to heart rate (HR) recording in young Korean men. METHODS: Twenty-nine healthy Korean men (24.0±2.0 yrs, 173.2±4.9 cm, 73.1±9.8 kg, body mass index 24.3±3.0 kg/m2, 16.4±5.7% body fat, waist-to-hip ratio 0.8±0.0, resting HR 68.3±6.6 bpm, VO2max 49.0±5.4ml/kg/min) volunteered to participate. Baseline and maximal oxygen consumption, and concomitant HR were measured. Three common physical activity questionnaires; International Physical Activity Questionnaire (IPAQ), Baecke Questionnaire of Habitual Physical Activity (BQ), Seven-Day Physical Activity Recall (S-PAR), were administered, and Bouchard Three-day Physical Activity Record (B-PAR) were completed by each subject in a recommended fashion. Using appropriate methods for each instrument, DEE and activity level were calculated. Three-day, 1-min interval HR using automatized HR monitor was recorded during the same time period of B-PAR, and subsequently recorded HR was translated to corresponding VO to calculated DEE while 1 liter of O assumed as 5 kcal. RESULTS: Estimated DEE by HR, IPAQ (n=20), S-PAR, and B-PAR was 3,232±809 kcal/d, 3,103±763 MET-min/wk, 3,057±439 kcal/d, and 3,110±490 kcal/d, respectively, and these measures were not different (ANOVA, P≥0.05). Physical activity indices by BQ was 7.6±1.1. The Pearson's correlation coefficient was only significant between B-PAR and BQ (r=0.400, P<0.05), B-PAR and S-PAR (r=0.621, P<0.01), and DEE by HR and IPAQ (r=0.484, P<0.05). Body mass index, % body fat, and waist-to-hip ratio were significantly correlated with DEE by S-PAR (r=0.793, 0.696, and 0.656, respectively, P<0.01) and B-PAR (r=0.606, 0.452, and 0.436, respectively, P<0.05), but not with IPAQ, BQ, and DEE by HR. CONCLUSIONS: Compared to HR recording, DEE obtained by four instruments evaluated in this study provided a reasonable group estimate for young healthy Korean men, although individual DEE among instruments was not identical. The questionnaires appeared to be valid and easy to administer in this population.