During the past 3.5 years the authors have evaluated 191 patients, both retrospectively and prospectively, to establish factors which might help to identify those patients at higher risk of developing pancreatic abscesses. Those factors included etiology of pancreatitis, number of severity indices present, and specific indices present. Once an abscess developed, severity indices, etiology, and bacteriology were examined as factors in mortality. Six specific severity indices occurred more often (P less than 0.05) in patients developing abscesses. These indices were lactate dehydrogenase evaluation, leukocytosis, metabolic acidosis, hypoxemia, hypocalcemia, and fluid sequestration. In addition, seven of 18 abscess patients had six or more indices present as opposed to five of 161 pancreatitis patients. This was significant at P less than 0.05 level. The etiology of the pancreatitis was not a significant factor. Once an abscess developed, gram-negative infections were polymicrobial (8 of 9 patients) and were associated with a 56 per cent mortality. The gram-positive abscesses (6 patients) were all monomicrobial and none of these patients died. In addition, age greater than 55 years, serum glucose greater than 200 mg%, hematocrit decrease of 10 per cent, and fluid sequestration greater than 6 L were associated with a 50 per cent or greater mortality. The authors believe that patients presenting initially with six or more severity indices, especially the six mentioned above, are at significantly increased risk for developing a pancreatic abscess and those abscess patients with gram-negative abscesses, as well as having any of the four severity indices previously mentioned, have a much worse prognosis.