Five patients with painful primary esophageal motility disorders underwent pharmacologic testing with isosorbide and hydralazine. While neither agent affected baseline amplitude or duration of distal esophageal contractions, pretreatment with hydralazine significantly blunted the response to bethanechol (mean esophageal contraction duration, 31.4 +/- 4.8 s after bethanechol alone vs. 12.7 +/- 1.8 s after bethanechol and hydralazine p less than 0.005). Premedication with isosorbide was significantly less effective. In addition, while all 5 patients experienced chest pain in response to bethanechol alone, only 1 of 5 experienced chest pain in response to bethanechol after previous hydralazine administration; 3 patients had chest pain after previous administration of isosorbide. Patients who were placed on long-term oral hydralazine therapy experienced improvement in chest pain and dysphagia with concomitant decrease in amplitude and duration of esophageal contractions on repeat motility study (176.5 +/- 23.8 mmHg to 97.3 +/- 27.0 mmHg, p less than 0.05, 7.5 +/- 0.8 s to 5.2 +/- 0.5 s, p less than 0.005). Hydralazine appears to be of value in the treatment of diffuse esophageal spasm and other painful primary esophageal motility disorders.