Based on in vivo studies on isolated muscle strips of the LES and on manometric in vivo studies on 8 mongrel dogs, 6 healthy volunteers, 6 patients with achalasia and 3 subjects with diffuse esophageal spasm we could demonstrate that nifedipine causes a long-lasting relaxation of smooth muscle, the esophagus and LES. In 8 dogs resting pressure at the LES was decreased by 20 mg nifedipine from 18.5 +/- 1.8 mm Hg to 8.2 +/- 0.9 mm Hg. This pressure decrease could not be reversed by pentagastrin stimulation (3.0 microgram/kg KG PG). The resting pressure in LES was decreased from 26.8 +/- 3.8 mm Hg to 16.4 +/- 2.1 mm Hg in healthy volunteers and from 45.5 +/- 2.6 mm Hg to 14.5 +/- 0.4 mm Hg in patients with achalasia. In 3 patients with diffuse esophageal spasm nifedipine (20 mg) caused a mean decrease of 38% of the contraction amplitude. Further clinical studies have to be done to clarify if the spasmolysis by nifedipine may be important in the treatment of spastic or hypertonic motility disorders of the LES and the esophagus.