Nonoperative management of blunt splenic trauma in adults is controversial despite numerous reports advocating this mode of therapy. Blunt splenic trauma is frequently managed without operation at our institution and, to define criteria that may predict a successful outcome, a retrospective review (1980 to 1988) of all adult splenic injuries was undertaken. Splenic injuries were documented by scintillation studies, CAT scanning, or at laparotomy. Sixty of 252 (24%) splenic injuries were initially treated without operation, which included bed rest, ICU monitoring, frequent physical exams, nasogastric tube, serial hematocrits, and follow-up splenic imaging. Five patients (5 of 60) failed nonoperative management and required interval laparotomy. Reasons for failure included blood loss greater than four units, enlarging splenic defect, or increasing peritoneal signs. Parameters predicting a successful outcome were localized trauma to the left flank or abdomen, hemodynamic stability, transfusion requirements less than four units, rapid return of GI function, age less than 60 years, and early resolution of splenic defects on imaging studies. No morbidity or deaths resulted from delayed operative intervention. In carefully selected adult patients, blunt splenic trauma may be successfully managed without operation.