It is known that lower esophageal sphincter (LES) pressure in patients with idiopathic achalasia is higher than in normal subjects, but in patients with Chagas' disease, who have esophageal disease with similar clinical, manometric, and radiologic results, studies of LES pressure show contradictory findings. We measured the LES pressure in 118 patients with chronic Chagas' disease, 14 patients with idiopathic achalasia, and 50 control subjects using a perfused catheter and the stationary pull-through (SPT) technique. The patients with Chagas' disease had normal esophageal radiologic examination (group A, N = 50), delay in esophageal clearance without dilatation (group B, N = 41), or delay in esophageal clearance with dilatation (group C, N = 27). The LES pressure of Chagas' disease patients of group A (18.6 +/- 9.1 mm Hg, mean +/- SD), group B (17.8 +/- 9.7 mm Hg), and group C (21.6 +/- 10.1 mm Hg) was lower (P less than 0.001) than the LES pressure of the controls (24.9 +/- 10.2 mm Hg). In patients with idiopathic achalasia, the LES pressure (40.7 +/- 17.8 mm Hg) was higher than in control subjects (P less than 0.01) and Chagas' disease patients (P less than 0.001). We conclude that the LES pressure of patients with Chagas' disease tended to be lower than that of control subjects and achalasia patients.