Twenty-three outpatients with chronic pancreatitis and severe exocrine insufficiency were studied for the purpose of comparing the effect of Pancrease, Pankreon, and Pankreatin by estimation of duodenal enzyme activity, the faecal fat excretion, and the faecal 14C-triolein-3H-oleic acid test and, at the same time, to evaluate these tests when monitoring outpatients. The three preparations did not disclose any significant difference in treating steatorrhoea. Pankreatin increased the meal-stimulated duodenal enzyme activity (p less than 0.01) and caused reduction in the faecal fat excretion (p less than 0.05), whereas no change in these variables were observed with Pankreon or Pancrease. The faecal 14C-triolein-3H-oleic acid test showed significant improvement in the 14C-triolein digestion with all three preparations (p less than 0.01). The faecal 14C-triolein-3H-oleic acid test was the most reliable when monitoring outpatients.