We conducted a retrospective study of patients younger than 20 years of age who had a diagnosis of chronic pancreatitis and underwent assessment at the Mayo Clinic between 1960 and 1990. Those with a known etiologic factor for the pancreatitis (such as a virus, trauma, alcohol, or hyperlipidemia) were excluded from the study. We compared the clinical course of the 42 patients who had hereditary pancreatitis (HP)--defined as at least two family members affected by the condition--with that of the 28 patients who had idiopathic pancreatitis (IP). The mean age at initial assessment was 7 years for those with HP and 12 years for those with IP. All patients in both groups had abdominal pain. Vomiting was more frequent in patients with HP than in those with IP; otherwise the initial symptoms were similar in both groups. Patients with HP, however, had more complications, including pseudocysts (seven patients), steatorrhea (four), ascites (three), portal hypertension (two), and diabetes (one), than did patients with IP (one each had diabetes, steatorrhea, and a pseudocyst). Complications or pain necessitated surgical intervention in 23 of 42 patients with HP versus 4 of 28 patients with IP. Overall in comparison with IP, HP seems to be a more severe variant of chronic pancreatitis, inasmuch as it is associated with more frequent complications and need for surgical intervention.