The optimum perioperative use of Intensive Care Unit (ICU) resources is not yet defined. We sought determine the effect of ICU admission on perioperative (30-day) and long term mortality. Methods: Observational study of all surgical cases in Scotland 2005-2007 followed-up until 2012. Patient, operative and care process factors were extracted. Primary outcome was perioperative mortality; secondary outcomes one and four-year mortality. Multivariable regression was used to construct a risk prediction model to allow standard-risk and high-risk groups to be defined based on deciles of predicted perioperative mortality risk, and to determine the effect of ICU admission (direct from theatre; indirect after initial care on ward; no ICU admission) on outcome adjusted for confounders. Results: 572598 patients were included. The risk model performed well (c-index 0.922). Perioperative mortality was 1125 (0.2%) in the standard-risk group (n=510979) and 3636 (6.4%) in the high-risk group (n=56785). Patients with no ICU admission within 7-days of surgery had the lowest perioperative mortality (whole cohort 0.7%; high-risk cohort 5.3%). Indirect ICU admission was associated with a higher risk of perioperative mortality when compared to direct admission for the whole cohort (20.9% vs 12.1%; adjusted OR 2.39, 95%CI 2.01, 2.84; p<0.01) and for high-risk patients (26.2% vs 17.8%; adjusted OR 1.64, 95%CI 1.37, 1.96; p<0.01). Compared with direct ICU admission, indirectly admitted patients had higher severity of illness on admission, required more organ support and had an increased duration of ICU stay. Conclusion: Indirect ICU admission was associated with increased mortality and increased requirement for organ support.