Calcium channel blockers and angiotensin converting enzyme-inhibitors are commonly used in the treatment of hypertensive renal transplant recipients. The purpose of this study was to investigate if the response rate to treatment differs with these drugs in this setting. A single centre, prospective, randomised, double-blinded, comparative study to address the efficacy of controlled release nifedipine or lisinopril in the treatment of hypertension (diastolic blood pressure > or =95 mmHg) in cyclosporin (CsA)-treated renal transplant recipients was performed. Recipients were randomised to receive either lisinopril (10 mg once daily) or controlled release nifedipine (30 mg once daily). The dose was doubled on indication. The number of responders (diastolic blood pressure <90 mmHg on monotherapy) were addressed during the early post-transplant phase (first 3 months) and during a late post-transplant phase (from 3 to 12 months after renal transplantation) in the same patient population. One hundred and fifty-four patients (nifedipine=78, lisinopril=76) with untreated hypertension (diastolic blood pressure> or =95 mmHg) were randomised within 3 wk after renal transplantation. One hundred and twenty-three patients (nifedipine=69, lisinopril=54) completed the study. Fourteen (20%) nifedipine-treated recipients responded during the early, and 26 (38%) during the late post-operative phase (months 4-12 after renal transplantation). Eleven (20%) lisinopril-treated recipients responded during the early, and 18 (33%) during the late post-transplant phase. Non-responders were, on average, 8.5+/-1.5 kg heavier both in the early phase and after 1 yr of treatment (p<0.01), and 6.1+/-0.9 yr older than responders (p<0.05). In conclusion, these results indicate that both controlled release nifedipine and lisinopril are equally efficient in the treatment of post-transplant hypertension. As monotherapy, both drugs show a "response rate" of 20-38%, depending on time interval after transplantation.