BACKGROUND Morbidly obese patients are at increased risk of hypoxemia during tracheal intubation because of increased frequency of difficult and impossible intubation and a decreased apnea tolerance. In this study, intubation with the GlideScope videolaryngoscope (GS) was compared with the Macintosh direct laryngoscope (DL) in a group of morbidly obese patients. METHODS One hundred consecutive patients (body mass index ≥ 35 kg/m(2) ) scheduled for bariatric surgery were randomized 1 : 1 to intubation with GS (group GS) or DL (group DL). The primary outcome was intubation time. Secondary outcomes were number of attempts, Cormack-Lehane grade, intubation difficulty scale score (IDS), subjective difficulty of intubation, desaturation, airway bleeding, postoperative sore throat, and hoarseness. Group assignment was not blinded. RESULTS Intubation in group GS and group DL lasted 48 (22-148) and 32 s (17-209), respectively (median (range); P = 0.0001); median difference 11 s (95% confidence interval 6-17). Laryngoscopic views were better in group GS with Cormack-Lehane grades 1/2/3/4 distributed as 35/13/2/0 vs. 23/13/10/4 in group DL (P = 0.003). IDS scores were significantly lower with GS than with DL. No other statistically significant differences were found. Two cases of failed intubation occurred in group DL vs. none in group GS (non-significant). Both patients were intubated with the GlideScope without problems. CONCLUSION Intubation of morbidly obese patients with GS was slightly slower than with DL. The increased intubation time was of no clinical consequence as no patients became hypoxemic. Both devices generally performed well in the studied population, but the GS provided better laryngoscopic views and decreased IDS scores.