OBJECTIVES: Achalasia patients are considered at increased risk for esophageal cancer, but the reported relative risks vary. Identification of this risk is relevant for patient management. We performed a prospective evaluation of the esophageal cancer risk in a large cohort of achalasia patients with long-term follow-up. METHODS: Between 1975 and 2006, all patients diagnosed with primary achalasia in our hospital were treated and followed by the same protocol. After graded pneumatic dilatation, all patients were offered a fixed surveillance protocol including gastrointestinal endoscopy with esophageal biopsy sampling. RESULTS: We surveyed a cohort of 448 achalasia patients (218 men, mean age 51 years at diagnosis, range 4-92 years) for a mean follow-up of 9.6 years (range 0.1-32). Overall, 15 (3.3%) patients (10 men) developed esophageal cancer (annual incidence 0.34 (95% confidence interval 0.20-0.56)). The mean age at cancer diagnosis was 71 years (range 36-90) after a mean of 11 years (range 2-23) following initial presentation, and a mean of 24 years (range 10-43) after symptom onset. The relative hazard rate of esophageal cancer was 28 (confidence interval 17-46) compared with an age-and sex-identical population in the same timeframe. Five patients received a potential curative treatment. CONCLUSIONS: Although the gastro-esophageal cancer risk in patients with longstanding achalasia is much higher than in the general population, the absolute risk is rather low. Despite structured endoscopical surveillance, most neoplastic lesions remain undetected until an advanced stage. Efforts should be made to identify high-risk groups and develop adequate surveillance strategies.