The pathology of chronic pancreatitis is reviewed in order to study the histology and incidence of pseudocysts in relation to the degree of pancreatic fibrosis and calcification. The series consisted of 57 resection specimens (49 partial pancreatectomy specimens and 8 total pancreatectomy specimens) and 9 autopsy pancreata. The histology of cystic lesions observed in the specimens was found to be identical to that of pseudocysts in acute pancreatitis. In 19 of 57, there was concomitant occurrence of focal autodigestive (fat) necrosis and pseudocysts. Pseudocysts were more common in specimens with focal fibrosis and few calcifications (13/25) than in those with diffuse advanced fibrosis and numerous calcifications (15/41). The findings indicate that sequelae of acute pancreatitis are frequently present in chronic pancreatitis, particularly in an early stage when fibrosis is still focal and calcification rare. This suggests that chronic pancreatitis may result from relapses of severe acute pancreatitis. A pathogenetic concept that relates acute pancreatitis with chronic pancreatitis is proposed.