The effect of pancreatic ductal and parenchymal changes on exocrine pancreatic function was analyzed prospectively in 75 patients with chronic pancreatitis (CP). Endoscopic retrograde pancreatography (ERP), computed tomography (CT), and serum pancreolauryl test (PLT) were performed to evaluate the degree of ductal, parenchymal, and functional changes, respectively. Results were evaluated by stepwise multivariate logistic regression and are expressed as the odds ratio (OR). A strong association was found between the degree of ductal changes in ERP and the degree of exocrine functional impairment (OR = 5.8). However, the association between the degree of parenchymal changes in CT and the degree of pancreatic dysfunction was weaker and was clearly confounded by the degree of ductal changes. On the basis of these findings, we suggest that the development of exocrine pancreatic functional impairment in patients with CP depends primarily on the degree of ductal changes, while parenchymal abnormalities play a less important role.