Ambulatory non-perfused oesophageal manometry was used to study oesophageal body function during consumption of a full meal in patients with achalasia. A measure of oesophageal body activity (the meal area index) was developed by calculating the total area under the pressure curve during eating, above the preprandial baseline oesophageal pressure, per meal minute. Untreated patients with achalasia (n = 13) were compared with normal subjects (n = 42), patients with benign stricture (n = 9) and patients with achalasia who had undergone Heller's myotomy (n = 17). The results showed a high meal area index in achalasia, due to a rise in baseline oesophageal pressure and frequent high-amplitude contractions during eating. This was not seen in normal subjects or patients with stricture. The high meal area index was abolished by successful Heller's myotomy but remained in two patients with persisting dysphagia. Sustained high intraoesophageal pressure is generated during consumption of a solid meal in untreated achalasia, resulting in a unique manometric profile. Manometry during eating using the meal area index permits quantitative assessment of oesophageal body function in achalasia and may aid in the assessment of response to treatment.