Plasma renin activity (P.R.A.) and plasma aldosterone were measured in twelve patients having hypopituitarism. Both mean values of this group were significantly lower than in normal subjects (P.R.A. recumbent: p less than 0.001, upright: p less than 0.001, plasma aldosterone: recumbent: p less than 0.02, upright: p less than 0.005). Hyporeninism is a controversed feature in hypopituitarism. Our preliminary data suggest that it is not directly correlated to ACTH or cortisol deficiency. Nevertheless it may explain the hypoaldosteronism prior reported in such patients.