A prospective study was performed in obese and nonobese patients undergoing lumbar spine surgery to report perioperative data and surgical outcomes. One hundred fifty-nine consecutive patients who underwent lumbar spine surgery by a single surgeon entered the study. Among 159 consecutive patients, 55 met the criteria for obesity (> 20% ideal body weight). The average weight was 226 lb in the obese group. There were 28 men and 27 women with ages ranging from 25 to 81 years, with a mean of 47.9 years. The diagnoses and procedures included 31% herniated nucleus pulposus with laminotomy and discectomy, 14% spinal stenosis with laminectomy, and 55% lumbar fusion procedures for other disorders. Twenty-nine percent had previous lumbar surgery that had failed. Results indicated that there were no significant differences between the obese and control groups in terms of duration of surgery (3.8 versus 3.2 h), blood loss (723 versus 605 ml), and duration of hospital stay (5.6 versus 5.8 days). The clinical results were 24% excellent, 40% good, 27% fair, and 9% poor in the obese group; and 27% excellent, 37% good, 19% fair, and 17% poor in the control group. This study found no significant differences between obese and control patients relative to blood loss, operative time, hospital stay, rate of complications, and functional outcome in lumbar spine surgery. Patient selection continues to be the most important factor in terms of operative success. We believe that lumbar spine surgery, including fusion, should not be withheld from obese patients who present with proper indications for surgery and fail an appropriate course of conservative treatment.