OBJECTIVE To determine the current practice in selected general practices for prescribing long term (> 6 months) treatment to suppress gastric acid secretion. METHODS Seven general practices in the Harrow area that always or usually refer to Northwick Park Hospital. METHODS 60,148 patients on lists of the general practices. METHODS Identification of patients receiving long term treatment through repeat prescribing data, followed by a manual and computer survey of patients' notes for indications and investigations. Patient compliance and views on treatment were sought by a postal questionnaire. METHODS Indications for treatment, treatment given, investigations undertaken before and during treatment. RESULTS 492 patients (0.82% of the population) were taking long term acid suppressing treatment. The most common diagnosis was duodenal ulcer disease (183 (37%) of all patients); oesophageal disease (118 (24%)) was also common. 93 patients (19%) were treated for abdominal pain where no diagnosis had been reached or who had only a diagnosis of gastritis on endoscopy. Ranitidine was prescribed in 394 (80%) patients. 298 (74%) patients found treatment helpful, but 108 (27%) had a poor understanding of their diagnosis. 317 patients (78%) took their drug as prescribed. 37 patients were also taking prescribed non-steroidal anti-inflammatory drugs and an additional 43 patients took regular aspirin or ibuprofen without prescription. CONCLUSIONS Long term acid suppressing treatment is common, and a substantial number of patients are taking these drugs long term without a diagnosis having been reached. It is hoped that protocols for investigation and treatment will improve these figures. Patients need to be better informed about their disease and the possible adverse effects of taking non-steroidal anti-inflammatory drugs in acid related upper gastrointestinal disease.