In order to evaluate the antihypertensive effectiveness and interaction with ciclosporin A (CS-A) nitrendipine, a dihydropyridine derivative calcium entry blocking agent, was used in 16 (13 men, 3 women) hypertensive renal posttransplant patients followed by the Nephrology Department of Hacettepe University Hospital. The patients did not receive any antihypertensive drug for a 7-day period. They were then given 20 mg/day nitrendipine for 3 weeks. At the end of this period, mean ( ± SE) supine blood pressure fell from 163/108 ± 3.6/1.87 to 141/87 ± 3.8/2.2 mm Hg (p < 0.01), while the heart rate was unchanged. 14 of 16 patients achieved full control of blood pressure levels with 20 mg/day nitrendipine, and only 2 patients needed a higher dosage of 30 mg/day (20 + 10 mg). After 3 weeks of treatment no significant variations in blood chemistry or renal functional parameters were noticed. There was also no difference between blood CS-A levels before and after treatment with nitrendipine (218.06 ± 33 vs. 222.68 ± 26 ng/ml, p > 0.05). We conclude that short-term therapy with nitrendipine in renal post-transplant patients does not appear to be harmful and longer term studies are needed to fully evaluate safety and efficacy of this drug. Because it influences neither blood chemistry nor renal functional parameters and blood CS-A level, it may be preferable to other calcium channel blocking agents in this group of patients.