To investigate the course of postprandial lipid solubilization in nine patients with chronic, alcoholic pancreatitis, luminal contents were aspirated from the proximal part of the jejunum for 180 min after a meal containing 1.5% fat. Six of the patients had pancreatic insufficiency, whereas three patients were without insufficiency. pH was measured continuously at two sites: at the level of the papilla of Vater and the aspiration site. The fraction of bile acids in the micellar phase of the jejunal aspirates correlated positively to both pH in the aspirates (p less than 0.05) and the fraction of fat solubilized (p less than 0.02). pH was below 4.0 for a longer period of time in the patients with insufficiency, compared to the patients without. However, pH fluctuated rapidly, and there was no correlation between the continuously measured values at the aspiration site and values in the aspirates. Lipid solubilization was not correlated to the lipase activity in the aspirates. We conclude that acidic bile acid precipitation most likely plays a dominant role in the pathophysiology of pancreatic steatorrhea although the methods available are too crude to disclose the precise course of events.