Acute pancreatitis (AP) is a very important cause of morbidity and mortality in Mexico.In 2001 AP was the 17th cause of death. Since 1994,the computed tomography (CT) scan was accepted for the screening of the severity (a) according to the Computed Tomography Severity Index (CTSI). In 2004 Mortele et al., developed a new tomography classification, Modified Computed Tomography Severity Index (MCTSI) including pancreatic and extra pancreatic disease, obtaining a very good correlation with those with organ failure. This study proposes compare the tomography classifications as indicators of severity. Cross-sectional study. Were included 30 patients with acute pancreatitis; APACHE II >= 8, non improvement with medical treatment and with initial mild pancreatitis,with addition of signs of complication in the first 72 hours of evolution, under CT scan, CTSIM and CTSI were compared. Statistical analysis using X2 test was calculated, kappa concordance coefficient(k) for the severity classifications. AP prevalence was 51.07%.Of the 30 patients including,19 man with mean age of 39.0 years (18-58 years),and 11 woman, with mean age of 50.9 years (22-82 years). The main causes were biliary pancreatitis in 16 cases (53.3%), and the second was alcohol,8 cases (26.7%). The kappa concordance coefficient for both tomography scans was 0.48 (p