AIM:A drcannual variation in the onset of several acute diseases, mostly dealing with cardiovascular system,has been reported. The present study was to verify the possible existence of a seasonal variability in the onset of acute pancreatitis. METHODS:All patients consecutively admitted to the Hospital of Ferrara,Italy,between January 1998 to December 2002, whose discharge diagnosis was acute pancreatitis,were considered.According to the time of admission,cases were categorized into twelve 1-mo intervals and in four periods by season.x~2 test for goodness of fit and partial Fourier series were used for statistical analysis. RESULTS:During the study period,549 cases of acute pancreatitis were observed.A significant peak of higher incidence was found in March-May,both for total population, males and subgroups with and without cholelithiasis or alcoholism.Fourier analysis showed the existence of a circannual rhythmic pattern with its main peak in March(95% CL.:February-April,P=0.005),and a secondary one in September.Death occurred more frequently in December- February,compared to the other periods(P=0.029),and chronobiologic analysis yielded a seasonal peak in November- December(P<0.001). CONCLUSION:This study shows the existence of a circannual variation in the onset of acute pancreatitis,with a significantly higher frequency of events in the spring,especially for patients with cholelithiasis or alcoholism.Moreover,events occurring during the colder months seem to be characterized by a higher mortality rate. AIM: A drcannual variation in the onset of several acute diseases, mostly dealing with cardiovascular system, has been reported. The present study was to verify the possible existence of a seasonal variability in the onset of acute pancreatitis. METHODS: All patients consecutively admitted to the Hospital of Ferrara, Italy, between January 1998 and December 2002, whose discharge diagnosis was acute pancreatitis, were considered. According to the time of admission, there were cases categorized into twelve 1-mo intervals and in four periods by season.x ~ 2 test for goodness of fit and partial Fourier series were used for statistical analysis. RESULTS: During the study period, 549 cases of acute pancreatitis were observed. A significant peak of higher incidence was found in March-May, both for total population, males and subgroups with and without cholelithiasis or alcoholism. Fourier analysis showed the existence of a circannual rhythmic pattern with its main peak in March (95% CL.: February - April, P = 0.005), and a secondary one in September. Death occurred more frequently in December-February, compared to the other periods (P = 0.029), and chronobiologic analysis yielded a seasonal peak in November-December (P <0.001). CONCLUSION: This study shows the existence of existence of a circannual variation in the onset of acute pancreatitis, with a significantly higher frequency of events in the spring, especially for patients with cholelithiasis or alcoholism. More over, events occurring during the colder months may to be characterized by a higher mortality rate.