Conventional treatment of pancreatic steatorrhoea in man has been unsatisfactory because 90% of the lipase content of therapy is inactivated by acid in the stomach and large doses of replacement treatment are needed to provide adequate supplementation. An acid stable agent (fungal lipase) was investigated in the treatment of pancreatic deficiency steatorrhoea in 11 pancreatectomised dogs maintained on a fixed dietary intake of fat and treated with pancreatin or fungal lipase. Ten grams (60,000 U lipase) of pancreatin was compared with 400mg (4800 U lipase) of fungal lipase administered with each meal against a no treatment group. There was no significant difference in stool bulk and faecal fat excretion between pancreatin and lipase treated animals. Both groups showed a significant reduction in stool bulk and fat excretion when compared with the no treatment group (p less than 0.01). A markedly diminished treatment volume, in the form of fungal lipase, is as effective in controlling steatorrhoea as pancreatin and may prove to be a potentially valuable therapy for patients with pancreatic insufficiency.