1. We have investigated the effect of intermittent doses of ammonia and octanoic acid on liver regeneration in the rat after partial hepatectomy. Regeneration was assessed by uptake of tritiated thymidine into liver deoxyribonucleic acid.
2. We have found a reduction in hepatic regenerative response in animals treated with ammonium acetate as a source of ammonia.
3. No inhibiting effect of octanoic acid on liver regeneration was found, at the dose used.
4. The implications of the results for management of fulminant hepatic failure are discussed.