A postal questionnaire on heartburn sent to 6760 randomly selected subjects yielded 3971 replies suitable for analysis. Heartburn had never been experienced by 1665 (42%) respondents. Significant symptoms of more than three months' duration that had occurred at least once a month in the preceding 12 months were reported by 1337 (34%) respondents. Of these, 875 had not consulted their general practitioner and were invited to attend for a structured interview with questionnaire and upper gastrointestinal endoscopy. A total of 177 were interviewed, and 143 underwent upper gastrointestinal endoscopy. Of those endoscoped, 106 (74%) experienced symptoms at least once a week. These were relieved by alginate consumption in 97 (68% of) cases. Just nine (6%) patients had been taking H2-receptor antagonists. Macroscopic appearances of oesophagitis were seen in 46 cases [13 (6%) grade 1, 24 (11%) grade 2, five (2%) grade 3, two (1%) grade 4, and two (1%) grade 5]. Three patients had mild strictures and six patients had Barrett's oesophagus. There were no appearances suggestive of malignancy. Biopsies were taken in 122 cases, including all those in which abnormalities had been seen. Histological evidence of oesophagitis was seen in 47 cases. Gastric metaplasia was found in six cases and dysplasia seen in three. Patients who self-medicate for reflux symptoms have a low prevalence of pre-neoplastic and neoplastic pathology. A substantial proportion, however, have histological evidence of oesophagitis and a small number have metaplasia.