Experimental models suggest that endothelin-1 (ET-1) has a significant role in the pathogenesis of cyclosporin A (CyA)-induced hypertension. However, its serum levels evaluated in different studies, including patients who received solid organ transplants, exhibited controversial results. Our study population consisted of 43 renal transplant patients: 33 were taking CyA as a component of their immunosuppressive regimen (CyA group) and 10 that were not taking CyA (control group). Baseline laboratory data, blood pressure and ET-1 levels were taken at baseline and 3 and 4 h after the ingestion of CyA. In the control group samples were collected in the corresponding periods of time. Blood pressure was significantly higher in the CyA group (mean blood pressure: 101.2 +/- 9.5 vs. 91.1 +/- 10.7 mmHg; p < 0.001), who also presented higher serum creatinine (1.2 +/- 0.28 vs. 0.97 +/- 0.13 mg/dL; p < 0.001) and ET-1 levels. In the CyA group an ET-1 peak was evident by the third hour after CyA ingestion that showed its maximum concentration after 1-2 h; the control group exhibited significantly lower levels of ET-1 (p = 0.044). ET-1 levels compared between patients with and without hypertension showed a non-statistically significant difference (1.54 +/- 0.76 vs. 1.27 +/- 0.62 ng/mL; p = 0.27, respectively). In conclusion, in the present study chronic CyA ingestion was associated with higher blood pressure and plasma ET-1 levels.