The prevalence and severity of cough during long-term enalapril treatment were examined by comparing a cohort of 136 hypertensive patients who started treatment with enalapril with consecutive age and sex-matched patients who commenced nifedipine therapy during the same period. Cough and other symptoms were assessed by a questionnaire designed to avoid bias towards reporting cough. After a mean of 27 months' treatment patients on enalapril had an excess of persistent cough (16 per cent, 95 per cent CI 7-25, p less than 0.01), voice change (14 per cent, 95 per cent CI 2-27, p less than 0.05) and sore throat (10 per cent, 95 per cent CI -0.1 to 20.3 per cent, p less than 0.01) when compared to nifedipine-treated patients. The cough was usually dry, moderate or severe, paroxysmal, and troublesome at night. Cough tended to be more common in women (23 per cent vs. 7.2 per cent), non-smokers, and at higher doses of enalapril, but was not related to age, duration of treatment, or chronic respiratory disease. Dry cough commonly persists as a troublesome side-effect during long-term enalapril treatment, and is often associated with voice change and sore throat.