Abstract： Background The prevalence of chronic pancreatitis has increased during recent years in Asia-Pacific areas as well as in China.The etiologies vary in different regions and periods.This study aimed to investigate the changing etiologies of chronic pancreatitis within 20 years at Peking Union Medical College Hospital in China.Methods Retrospective analysis of the etiologies of 636 cases of chronic pancreatitis at Peking Union Medical College Hospital from 1990 to 2010 was performed.Patients were divided into two groups according to two time periods (1990-2000 and 2001-2010).Statistical analysis was performed using the chi-square test.Results The morbidity rate of chronic pancreatitis in China has recently increased.The main etiology changed from biliary diseases in the 1990s (decreased from 36.8％ to 28.1％) to alcohol abuse after the year 2000 (increased from 26.5％ to 36.8％).The main etiology of biliary diseases is stones in the cholecyst or bile duct,and the percentage of cholecystitis cases has increased.Autoimmune disease,including autoimmune pancreatitis,has increased quickly and currently accounts for 7.3％ of cases because a greater number of autoimmune pancreatitis cases are being diagnosed.Approximately 9.5％ of chronic pancreatitis cases are caused by multiple factors such as alcohol abuse and bile duct stones.Other factors include cholecystectomy and acute pancreatitis.Conclusions The main etiology of chronic pancreatitis has changed from biliary disease to alcohol abuse in recent years.Autoimmune factors have also obviously increased.