BACKGROUND & AIMS Achalasia is a disorder of esophageal motility with a reported incidence of 0.5 to 1.6 per 100,000 persons per year in Europe, Asia, Canada, and America. However, estimates of incidence values have been derived predominantly from retrospective searches of databases of hospital discharge codes and personal communications with gastroenterologists, and are likely to be incorrect. We performed a cohort study based on esophageal manometry findings to determine the incidence of achalasia in South Australia. METHODS We collected data from the Australian Bureau of Statistics on the South Australian population. Cases of achalasia diagnosed by esophageal manometry were identified from the 3 adult manometry laboratory databases in South Australia. Endoscopy reports and case notes were reviewed for correlations with diagnoses. The annual incidence of achalasia in the South Australian population was calculated for the decade 2004 to 2013. Findings were standardized to those of the European Standard Population based on age. RESULTS The annual incidence of achalasia in South Australia ranged from 2.3 to 2.8 per 100,000 persons. The mean age at diagnosis was 62.1 ± 18.1 years. The incidence of achalasia increased with age (Spearman rho, 0.95; P < .01). The age-standardized incidence ranged from 2.1 (95% CI, 1.8-2.3) to 2.5 (95% CI, 2.2-2.7). CONCLUSIONS Based on a cohort study of esophageal manometry, we determined the incidence of achalasia in South Australia to be 2.3 to 2.8 per 100,000 persons and to increase with age. South Australia's relative geographic isolation and the population's access to manometry allowed for more accurate identification of cases than hospital code analyses, with a low probability of missed cases.