This study evaluated the new criteria for the diagnosis of chronic pancreatitis (CP) with endoscopic retrograde pancreatography (ERP) proposed by the Japan Pancreas Society in 1995 by comparing it with the older criteria of the Japanese Society of Gastroenterology proposed in 1983. No significant differences were noted between the two when the diagnostic sensitivity of ERP was considered in calcifying CP. Among 54 patients of noncalcifying CP (group I) with ERP diagnosis of moderate or advanced pancreatitis by the previous criteria, only one of 22 with the localized type was definite CP. The remaining 21 were ruled out as either definite or probable CP, and six were classified as having chronic obstructive pancreatitis based on the new criteria. In contrast, a diagnosis of definite CP was made not only for all the 32 patients with CP (group I) of diffuse type but also in 11 cases of CP (group II) with diffuse minimal pancreatitis showing irregular dilatation of the side branches with scattered distribution throughout the gland. In a series of 15 follow-up patients with CP (group II) having initial ERP diagnosis of minimal pancreatitis, CP group I developed in three of five cases of diffuse minimal pancreatitis, which is consistent with definite CP by the new criteria, whereas progression to this group of CP was found in none of the 10 patients with localized minimal pancreatitis. These results indicate that although localized CP is excluded from CP, the incidence of diffuse noncalcifying CP diagnosed by ERCP was increased with the new criteria, and detecting radiologic features with diffuse irregular dilatation of the branch ducts based on these criteria may lead to early diagnosis of CP.