To determine if patients who have undergone uneventful vascular surgery (VS), nonvascular intracranial surgery (ICS), or anterior cervical laminectomies (ACL) have enough serious postoperative problems to justify routine overnight observation in an intensive care unit (ICU), we recorded every problem and associated therapy administered to 263 such patients within 36 h of ICU admission. The severity of each treated problem was graded from 1 (safe to delay treatment for at least 2 h) to 4 (life-threatening, immediate treatment required). Defining patient benefit from the ICU as treatment for one grade 4 problem or more than one grade 3 problem, 44% of VS patients (N = 177), 14% of ICS patients (N = 73), and none of the ACL patients (N = 13) benefited. We conclude that these percentages justify an overnight ICU stay for all VS patients, especially as the occurrence of serious problems was unpredictable and most serious problems were still being treated 4 h postoperatively. Furthermore, routine ICU admission of all patients in the groups studied would reduce patient costs if only 13 of the 88 patients who benefited were prevented from becoming critically ill.