In order to evaluate the effects of leanness on autonomic regulatory functions, resting metabolism, width of the middle finger veins, daily activity, and urinary catecholamine, as well as their metabolite, vanylmanderic acid (VMA), excretions were compared in young normal and lean women. It was observed in lean subjects that resting metabolism was significantly higher. Urinary excretions per kg body weight of dopamine (DA) and noradrenaline (NA) were significantly larger in lean subjects than control ones, while those of adrenaline and VMA tended to be larger in the lean group. Both NA/DA ratio and VMA/NA ratio did not differ between groups. It is surmised from the present results, concomitant with those from a previous study, that an increased protein intake might improve modified autonomic regulatory functions, probably via a suppression of excess sympathetic activity observed in lean subjects.