OBJECTIVE Intra-abdominal infection in severe acute pancreatitis (SAP) has significant morbidity and mortality; however, reports conflict on the outcome of patients with intra-abdominal fungal infection (IFI). We aimed to compare the morbidity and mortality of IFI compared with intra-abdominal bacterial infection (IBI) and no intra-abdominal infection (NII) in patients with SAP. METHODS Medical records of 207 consecutive patients admitted with SAP (per the Atlanta classification) to the Mayo Clinic (Rochester, Minnesota) between 1992 and 2001 were reviewed. All intra-abdominal microbiology cultures from pancreatic and peri-pancreatic necrosis, abscess, and/or pseudocyst obtained at operation, endoscopic necrosectomy or computed tomography-guided aspiration were reviewed. Patients were divided into three groups-IFI, IBI, and NII. Primary fungal infections were those for which there had been no prior abdominal interventions, and secondary infections were those that followed a prior intervention. Our main outcome was in-hospital mortality and secondary outcomes included the presence of organ failure (OF), need for surgical intervention, need for intensive care unit (ICU) care, and duration of hospitalization. RESULTS The groups were similar in terms of baseline characteristics, use of prophylactic antibiotics, use of enteral/parenteral nutrition, development of necrosis, and peripancreatic fluid collections. Fifty-two percent of patients had an intra-abdominal infection; all of these developed bacterial infections and 30 (15%) developed concomitant fungal infections. There were 7 primary fungal infections and 23 secondary infections-no important outcome differences were noted between these groups. Compared with patients with IBI, patients with IFI had longer hospital (63 vs. 37 days, P<0.01) and ICU (28 vs. 9 days, P<0.01) stays and higher rates of OF (73 vs. 47%, P<0.04), but similar mortality rates (20 vs. 17%, P0.41). Multivariate analysis revealed the presence of OF (odds ratio (OR) 2.4, 95% confidence interval (CI) 1,7) and the need for ICU care (OR 4.3, 95% CI 1,28) to be associated with IFI. CONCLUSIONS Patients with SAP and IFI suffered greater in-hospital morbidity than did patients with IBI alone. Concomitant fungal infection, however, did not increase the in-hospital mortality rate.