Renal transplant patients die prematurely of cardiovascular disease and LV hypertrophy is now recognised as an important adverse prognostic indicator. This study investigated the factors implicated in the development of echocardiographic abnormalities (including LV hypertrophy) and the possible differential effects of treatment with cyclosporin and azathioprine. A cross-sectional study was undertaken in 46 patients randomly assigned to immunosuppressant treatment with either cyclosporin or azathioprine at 1 year post-transplantation: patients were studied not less than 5 years after assignment to cyclosporin (CyA) - or azathioprine (Aza)-based treatment regimens. Although clinic blood pressure control was not different in the two treatment groups, 24 hour ambulatory BP (ABP), particularly night-time BP, was significantly higher in the CyA group. There was a trend for both left ventricular hypertrophy (61 vs. 43%) and carotid wall thickening (43 vs. 26%) to be more common in the CyA group though this failed to achieve statistical significance. Left ventricular mass was determined by ABP, rather than clinic BP, and was also associated with increased QT dispersion. Multivariate analysis identified that 24 hour ambulatory systolic blood pressure (ASBP) and time on renal replacement therapy (RRT) were the major determinants of LV mass. Thus, despite the absence of differences in clinic BP measurements, CyA treatment was associated with higher rates of cardiovascular functional and structural abnormalities. This small scale study has identified cardiovascular functional and structural abnormalities in renal transplant patients, particularly in those receiving CyA-based immunosuppressive therapy. However, rather than reflecting a direct effect of CyA they are related to increased 24 ABP (but not clinic BP). These data suggest that ABP should be used to monitor and target antihypertensive therapy in this high risk patient group. Moreover, the future use of non-calcineurin inhibitor immunosuppressant therapy may have benefits on blood pressure control and LV mass.