Basal plasma concentrations of thyroxine (T4), 3,3',5-triiodothyronine (T3), free T4 index (TF4I), free T3 index (FT3I) reverse T3, 3,3',5-triiodothyronine (rT3), resin T3 uptake (TR3U), thyroxine-binding globulin (TBG), thyrotropin (TSH), prolactin (PRL) and growth hormone (GH) as well as thyrotropin releasing hormone (TRH) stimulated TSH, PRL and GH were investigated in 31 consecutive male patients (mean age 41 years) with chronic alcoholism. According to the histology of their liver biopsies the patients were divided into three groups: patients with normal livers, steatosis and cirrhosis. The control group consisted of 30 healthy males. The patients had abstained from alcohol for at least one week when studied, and they were on a nutritionally adequate diet. All had consumed a daily minimum of 52 g ethanol for at least 5 years. None of the patients had severe or decompensated liver disease. The patients had significantly reduced T3 and rT3 plasma levels compared to normals. Patients with cirrhosis of the liver had increased TBG and normal RT3U levels, while those without cirrhosis had increased RT3U and normal TBG levels. Plasma concentrations of basal as well as TRH-stimulated TSH and PRL were unchanged in alcoholic patients, whereas basal as well as stimulated GH levels were increased in cirrhotic alcoholics. It is concluded that alcohol per se influences T3 levels, but not the part of the hypothalamic-pituitary axis studied, and that the binding proteins are mostly determined by the degree of liver disease.