BACKGROUND: There is growing interest in collaborative management of surgical patients. However, few data describe how medical consultation influences quality of care or resource use. The objective of this study was to determine whether medical consultation improves care in surgical patients. METHODS: Observational cohort of patients undergoing surgery between May 1, 2004, and May 31, 2006, at a university-based hospital. The outcomes included costs, hospital length of stay, use of preventive therapies (such as perioperative beta-blockers) and clinical outcomes. RESULTS: Of 1,282 patients, 117 (9.1%) underwent a perioperative medical consultation. Consulted patients were of a similar age, sex, and race, but more frequently had an American Society of Anesthesiologists score of 4 or higher (34.2% vs 13.0%; P < .001), diabetes mellitus (29.1% vs 16.1%; P < .001), vascular disease (35.0% vs 10.6%; P < .01), or chronic renal failure (23.9% vs 5.6%; P < .001). After adjusting for severity of illness and likelihood of receiving a consultation, patients were just as likely to have a serum glucose level of less than 200 mg/dL (<11.1 mmol/L), receive perioperative beta-blockers, or receive venous thromboembolism prophylaxis. Consulted patients had a longer adjusted length of stay (12.98% longer; 95% confidence interval, 1.61%-25.61%) and higher adjusted costs (24.36% higher; 95% confidence interval, 13.54%-36.34%). Patients who had a consultation from a generalist did not receive different quality of care, but had costs and length of stay similar to nonconsulted patients. Our results may be influenced by unaccounted referral bias or severity of illness. CONCLUSIONS: Perioperative internal medicine consultation produces inconsistent effects on efficiency and quality of care in surgical patients. Modifying the consultative model may represent an opportunity to improve care.