When rats received dimethylnitrosamine every 24 h until death, plus hormone treatment after the first 24 h, the survival was enhanced between 100 and 140 h compared with the control rats, with attenuated derangements of prothrombin time and serum albumin levels at 120 h. In rats given a single dose of dimethylnitrosamine, hepatic DNA synthesis peaked at 48 h. The synthesis was increased after hormone treatment when started immediately, but not when delayed for 24 h. Hormone treatment for 3 days starting 24 h after a single dose of dimethylnitrosamine produced a rapid normalization of decreased hepatic protein content on day 9, although hepatic DNA content was not affected. These results suggest that this treatment is effective for hepatic failure, and the promotion of restoration of liver function is a contributing factor to its effect, in addition to the stimulation of hepatocyte proliferation.