Energy intake, body weight and resting metabolic rate (RMR) were measured on seven days consecutively, in 20 men and 14 women on ad libitum food intake under free-living conditions. These measurements were repeated in 8 men and 9 women twice with an interval of two months. Mean energy intake (EI) as measured by 'Weightment' method, was 2820 +/- 577 kcal/d in men and 1611 +/- 147 kcal/d in women. EI showed significant differences between weeks (P less than 0.01, CV = 13.1% in men and 9.5% in women) and between subjects (P less than 0.05, CV = 13.7% in men and 9.8% in women). Intra individual variance contributed up to 60 to 70 per cent of the total variance in EI in both the groups. RMR measured by using Oxylog, varied between the three periods (CV = 6% in men and 5.9% in women) and between subjects (CV = 5.7% in men and 12.3% in women). Mean RMR of both men and women was lower than the predicted value by FAO/WHO/UNU equation. Estimate of mean 24 h energy expenditure, using activity diary and factorial method, in the first round was 2458 +/- 144 kcal in men and 1655 +/- 172 in women, resulting in an energy balance of 308 kcal in men and -44 kcal/d in women. The pattern of activity remained the same in the three rounds for both groups. There were no significant changes in weight (CV-1.6%) or per cent body fat during the study period (P greater than 0.1).