The records of 230 adhesive small bowel obstruction (ASBO) episodes in 181 patients have been reviewed to observe the place of conservative treatment and to establish criteria to predict the success of conservative trial. Immediate operation has been reserved for 81 episodes that have presented with fever and leucocytosis and/or localized abdominal tenderness, or complete obstruction. The remaining 149 episodes have initially undergone conservative trial. Although 110 episodes (73.8%) have been cured with conservative trial, 39 (26.2%) subsequently necessitated surgical intervention. No adverse occurrences have been observed during or after delayed operations. There was no strangulated bowel nor mortality both in delayed operation and conservatively treated groups. Recurrence has occurred with rate of 18.75% and 36.47% after surgery and conservative treatment, respectively, being significantly different (P less than .01), but the treatment method of the previous episode has been without influence on the method used in the recurrent obstruction (P less than .05). Among the assumed predictive criteria, age at recent laparotomy (P less than .02), time elapsed between recent laparotomy and obstructive episode (P less than .01), the primary condition necessitating laparotomy (P less than .01), the incision of previous laparotomy (P less than .05), and duration of conservative trial (P less than .01) correlated significantly with the success of conservative trial. The number of previous laparotomies and obstructive episodes (P less than .05) have not showed correlation. By the conservative approach used in selected patients with ASBO, 40% overall have been spared operation, without any adverse occurrences. Using the proposed criteria, the success rate of conservative treatment can be predicted.