With the renewed interest in esophageal motility disorders, diffuse esophageal spasm is being diagnosed more frequently. In many clinical settings, however, the term is used as a synonym for noncardiac chest pain. Our review of the literature and broad clinical experience in studying the motility patterns of healthy subjects have helped us better define diffuse esophageal spasm. The diagnosis of diffuse esophageal spasm should be considered only in symptomatic patients showing simultaneous contractions after wet swallows during esophageal motility testing. Simultaneous contractions should occur after at least 10% of swallows and be intermixed with normal peristaltic contractions. Repetitive waves, contractions of prolonged duration, spontaneous activity, high-amplitude contractions, and lower esophageal sphincter abnormalities may be seen in diffuse esophageal spasm. None of these findings alone or in combination justifies a diagnosis of diffuse esophageal spasm unless associated with simultaneous esophageal contractions.