To determine the resting metabolic rate in a sample of the Italian population, and to evaluate the validity of predictive equations for resting metabolic rate (RMR) from the literature in normal and obese subjects. Design: Cross-sectional observational study. Settings: Department of Human Physiology and Nutrition, University 'Tor Vergata', Rome. Subjects: A total of 320 healthy subjects, 127 males and 193 females, aged 18-59 y. Methods: Weight, height and resting metabolic rate by indirect calorimetry were measured. Resting metabolic rate was also predicted using equations from the literature. Results: Resting metabolic rate (mean ± s.d.) in normal weight subjects was 7983 ± 1007 kJ/24h (males) and 6127 ± 907 kJ/24 h (females). Measured RMR and predicted RMR values using various equations from the literature were significantly different in males and females, except for the Harris-Benedict equation and the Schofield equations. Also, in overweight and obese subjects the prediction error was generally larger compared to normal-weight subjects for all formulas except for the Harris-Benedict and Schofield formulas. In overweight and obese males but not in females, RMR was lower than in normal-weight subjects after correcting for weight and age differences. Stepwise multiple regression of resting metabolic rate against weight, height and age in males and females did not reveal a prediction formula with a lower prediction error than the Harris-Benedict or Schofield formulas and thus was not further explored. Conclusions: The Harris-Benedict formula and the Schofield formula provide a valid estimation of resting metabolic rate at a group level in both normal-weight and overweight Italians. However, the individual error can be so high that for individual use a measured value has to be preferred over an estimated value.