The effect of 10 mg of sublingual nifedipine on the lower esophageal sphincter pressure (LESP) was studied by continuous perfusion manometry in 15 Chagasic patients and 9 controls. Resting LESP was lower in Chagasic patients (13.51 +/- 2.37 mmHg) than in controls (19.60 +/- 2.51 mmHg, P less than 0.02). Nifedipine caused a gradual decrease in the LESP in both Chagasics and controls. Maximal reductions occurred 50 minutes after the drug administration when LESP was reduced to 60% of the resting LESP in the control group and to 43% in the Chagasic group. These results indicate that the striking abnormalities found in the intramural plexuses of the alimentary canal of Chagasic patients do not affect the responsiveness of LESP to nifedipine, and that nifedipine may be useful to reduce LESP in Chagasic megaesophagus.