Thirty morbidly obese patients presenting for bariatric surgery were evaluated for symptomatic and objective evidence of gastroesophageal reflux. Sixteen patients had heartburn while 14 were asymptomatic. All underwent esophageal function testing; manometry was performed in all patients, pH monitoring in 28. Patients with esophageal pH < 4 for more than 5% of observed time weighed more than those with normal acid exposure, 165.2 vs 129.8 kg (P < 0.01), and had significantly higher body mass indices, 56.5 vs 48.3 kg/m2 (P < 0.05). Similarly, morbidly obese patients with abnormal reflux scores weighed significantly more and had greater body mass indices than patients with normal scores (P < 0.05). Lower esophageal sphincter pressure was higher in patients with normal esophageal acid exposure than in those with abnormal findings, 15.5 vs 12.5 mm Hg (P < 0.05). This study demonstrates a correlation between both weight and body mass index with gastroesophageal reflux.