Background & Aims: Manometry is used widely in the evaluation of esophageal disorders. Our aim was to assess the intra- and interobserver reliability of esophageal manometry and identify potential causes for diagnostic variability. Methods: Seventy-two esophageal manometry tracings were selected randomly from archives. Eight interpreters randomly and blindly evaluated tracings. Interpreters were divided into 3 groups: highly experienced (N = 3), moderately experienced (N = 3), and inexperienced (N = 2). Each tracing was examined for abnormalities involving the lower-esophageal sphincter (LES) and esophageal body. Interpreters rendered a single diagnosis from a list of 7 manometric diagnoses: normal, nutcracker, hypertensive LES, hypotensive LES, diffuse esophageal spasm (DES), nonspecific/ineffective esophageal motility (IEM), and achalasia. Intra- and interobserver agreements were determined and reasons for varied diagnoses were investigated. Results: Overall intraobserver agreement was good (κ = .63, P < .0001). There was no difference ( P = .9) between the highly and midexperienced interpreters (κ = .61 and .65, respectively). Interobserver agreement for the diagnosis of achalasia and normal motility was good (κ = .65 and .56, respectively). However, other manometric diagnoses yielded only fair interobserver agreement (κ = .27). DES, nonspecific/ineffective esophageal motility (IEM), and hypo- and hypertensive LES diagnoses showed the least agreement. Poor adherence to established manometric criteria, misinterpretation of intrabolus pressure, and technical inadequacy were the most common sources of inconsistency in interpretations. Conclusions: Manometric diagnoses of conditions other than normal or achalasia are variable and have poor interobserver variability. Given their uncertain clinical implications, we must either redefine them or eliminate them from practice.