BACKGROUND: Morbid obesity is generally considered to be a surgical and anesthetic risk. Some surgeons have advised the routine use of invasive monitoring for morbidly obese individuals undergoing surgery. The purpose of this study was to identify morbidly obese individuals undergoing primary gastric bypass procedures who required central or other forms of invasive monitoring for their management. METHODS: We reviewed a series of 521 morbidly obese individuals undergoing consecutively performed primary vertical banded gastroplasty-gastric bypasses, a form of gastric bypass (performed at two community hospitals), for patients who had central, arterial, or urinary catheters placed during their hospital course for monitoring purposes. The patient population was also analyzed for age, preoperative co-morbidities, body mass index, length of operation, and for whether technical complications were encountered intraoperatively. RESULTS: At one of the two hospitals, 10% of patients had arterial catheters placed intraoperatively. In each case, the catheters were removed in the recovery room. At the second hospital, no patient had invasive monitoring intraoperatively. In the entire study group, only five patients required the use of invasive monitoring postoperatively. In each of these patients, technical perioperative complications occurred. The five patients and two hospital groups did not differ significantly in age, sex, number of co-morbidities or preoperative BMI from the study group as a whole. CONCLUSION: Morbid obesity itself is not an indication for invasive monitoring. The majority of morbidly obese individuals can be safely managed through primary gastric bypass procedures without invasive monitoring.