Twenty-two patients (mean age, 48.5 years) suspected of early chronic alcoholic pancreatitis, who had ductal changes mainly in the side branches, were followed by serial endoscopic retrograde pancreatography (ERP). Follow-up ranged from 1.1 to 11.9 years (mean, 5.4). Serial ERP revealed deterioration in six patients (27%), five of whom had outflow disturbance of the main pancreatic duct. On the other hand, five patients presented slight progressive changes restricted to the side branches and the remaining 11 patients showed no change. None of the 12 patients who abstained from drinking showed a deterioration of their pancreatogram. The deterioration of clinical symptoms was less frequently seen in patients with abstinence (5/12) than in those who continued drinking (10/10). This study suggests that a ductal abnormality mainly in the side branches may be an early sign of chronic alcoholic pancreatitis. Outflow disturbance of the main pancreatic duct might play an important role in the progression of the pancreatogram to an advanced stage. Abstinence is associated with a high probability of stabilization of both clinical symptoms and ductal changes.