Since dry cough has recently been recognized as a side effect of angiotensin converting enzyme (ACE) inhibitors employed in the treatment of hypertension or congestive heart failure, the incidence of dry cough in elderly patients receiving ACE inhibitors was investigated. There were 237 out-patients on either captopril, enalapril, or delapril, in August and November 1989. Questionnaires concerning dry cough and smoking were completed by 184 patients. Patients either less than 50 years of age, or with chronic pulmonary disease were excluded. The remaining 168 patients, 63 males, 105 females, with a mean age of 73 years were analyzed for the incidence of a dry cough in relation to age, sex, smoking, and type of drugs. The overall incidence of a dry cough was 21/168 (12.5%), 7/63 (11.1%) for males and 14/105 (13.3%) for females, and was less frequent with advancing age; in the 51-60 age group 4/11 (36.4%), in the 61-70 age group 5/39 (12.8%), in the 71-80 age group 9/75 (12.0%), in the 81-90 age group 3/40 (7.5%), in the 91- age group 0/3 (0%). Enalapril showed significantly higher incidence of dry cough than captopril (16/93, 17.2% vs 7/88, 8.0%, p less than 0.05). Delapril showed an incidence 4/11, 36.4%, however, 9 out of the 11 patients who were given delapril had had a history of a dry cough with captopril or enalapril, and in 4 out of these 9 patients the dry cough disappeared by replacement of captopril or enalapril by delapril.(ABSTRACT TRUNCATED AT 250 WORDS)