Hypertension is a major risk factor for stroke and heart disease in elderly people. Eighty hypertensive subjects with mild cognitive impairment, aged over 70 years were drawn from a community screening programme and randomized to either captopril 12.5 mg twice daily or bendrofluazide 2.5 mg daily in a double-blind trial. Subjects were excluded if they had previously received antihypertensive treatment or had significant cardiac disease. Electrocardiograms (ECG) were recorded and scored at baseline and after 12 and 24 weeks of treatment. Mean blood pressure fell significantly and equally in both treatment groups. Most ECG variables remained unchanged throughout the trial but a significant reduction in QRS duration from 0.08 to 0.07 seconds was observed with captopril at 12 weeks (p = 0.004) and 24 weeks (p = 0.002). Subjects on captopril also exhibited a significant improvement in overall ECG classification at 12 weeks (p < 0.05), although this was not sustained at 24 weeks (p = 0.076). Captopril is a suitable alternative to bendrofluazide as an antihypertensive drug for elderly people with regard to ECG detected cardiac complications.