Thirteen diabetic patients with hypertension (mean diastolic blood pressure 96.2 +/- 1.1 mmHg) were included in a study to assess the effects of lisinopril (20 mg day-1) on measures of nerve function. Patients had nerve conduction velocity (NCV), temperature discrimination threshold (TDT), and vibration perception threshold (VPT) measurements. At the end of 12 weeks of treatment with lisinopril, there was a significant improvement in median motor NCV (mean change +/- SEM 2.7 +/- 0.6 m s-1, p < 0.0001), median sensory NCV (2.1 +/- 0.9 m s-1, p = 0.03), peroneal motor NCV (1.0 +/- 0.4 m s-1, p = 0.03), and sural sensory NCV (1.9 +/- 0.7 m s-1, p = 0.01) values. There were also significant improvements in warm TDT and VPT. Diastolic BP decreased significantly, but there was no significant change in HbA1. Double blind controlled studies are now needed to confirm the effect of lisinopril on measures of nerve function.