Probably the most common and irritating side effect of angiotensin-converting enzyme (ACE) inhibitors is cough. In this retrospective study the incidence of cough was investigated in 1113 patients with arterial hypertension who were receiving ACE inhibitors alone or in combination with other antihypertensive agents. Patients were treated with one of the following ACE inhibitors: enalapril 10-20 mg/day (n:668), captopril 25-75 mg/day (n:234), perindopril 2-8 mg/day (n:90), or lisinopril 5-20 mg/day (n:121). Mean follow-up periods were twenty-six months with enalapril, twenty-nine months with captopril, eleven months with perindopril, and thirteen months with lisinopril. Spontaneously declared cough incidence in enalapril, captopril, perindopril, and lisinopril groups were 7%, 5.1%, 2.2%, and 1.6%, respectively. Cough was not dose related. Treatment was stopped in all patients with cough. In 59% of patients the onset of cough occurred after the first month of treatment (thirty to one hundred eighty days). Cough decreased by 50% within three days of drug cessation and disappeared in ten days. Mean age of patients with cough was 58.7 years and 79% of them were women. In patients without cough, mean age was 57.8 years and 56% of them were women. There was no significant difference between the two groups regarding mean age, but the sex difference between groups was statistically significant (P < 0.05).