There are no requirements concerning the amplitude of simultaneous contractions among the present criteria for the manometric diagnosis of diffuse esophageal spasm. The purpose of this investigation was to determine whether the current criteria effectively identify an appropriately homogenous patient population. Sixty consecutive motility tracings that met the criteria for diffuse esophageal spasm were evaluated. A bimodal distribution of the highest simultaneous esophageal contraction for each patient was observed. One group's (N = 29) highest simultaneous esophageal contractile amplitude was < or = 74 mm Hg, the other's (N = 31) highest simultaneous esophageal contractile amplitude was > or = 100 mm Hg. Group 1 had significantly decreased lower esophageal sphincter pressure, lower peristaltic amplitude, more aperistalsis, fewer simultaneous contractions, and fewer complaints of chest pain. These comparisons suggest that consideration be given to the amplitude of simultaneous esophageal contractions in the manometric diagnosis of diffuse esophageal spasm.