Impairment of hemodynamics and metabolism, which is determined by the condition of the hypothalamo--hypophyseal-adrenal system, is very important in the pathogenesis of peritonitis. The cortisol content, the activity of plasma renin, aldosterone, T3 and T4 were studied in 50 patients with diffuse and generalized peritonitis. The regional control group was formed of 50 practically healthy individuals. The patients were examined on the 1st, 3rd, 7th, and 14th postoperative days. The "low T3" syndrome in considerable increase of the content of cortisol, which inhibits the production of triiodothyronine directly, was encountered during the entire postoperative period in patients with peritonitis. Hyporenin hyperaldosteronism occurred on the 7th-14th day, which was evidenced of distorted physiological mechanisms of the production of mineralocorticoids in peritonitis. The hormonal dysbalance in the examined patients was greatest of the 7th postoperative day; the content of the studied hormones was partly normalized by the 14th day.