Body fat, total body water and totally body nitrogen were estimated twice before and after refeeding in 32 patients with anorexia nervosa. Body composition was estimated once in 29 normal controls using the techniques of anthropometry, impedance and IVNCA. The influence of weight gain and other variables, ie psychological status, biochemical parameters, exercise and dietary composition, on protein repletion was examined. Methods of assessment of body composition were compared. The results demonstrated that in anorexia nervosa patients, protein was more completely replenished than fat when patients had reached 85% of average body weight for height and age. Weight gain was the only determinant of protein gain. There was no correlation with psychological, biochemical or exercise status nor with dietary composition. Direct methods, ie deuterium dilution and IVNCA, were shown to be preferable in determination of body composition in anorexia nervosa.