Recent reports indicate a high prevalence of left ventricular hypertrophy (LVH) in children on dialysis and after renal transplantation (Tx), as identified by cross-sectional analysis. However, the evolution of LVH in pediatric patients with end-stage renal disease after renal Tx is not well established. To assess changes of left ventricular mass (LVM), we prospectively performed echocardiography in 23 children and adolescents between November 1998 and July 2000. Each patient had an echocardiographic evaluation while on dialysis (for at least 6 weeks) and a follow-up evaluation at least 6 months after successful renal Tx (i.e. with a measured glomerular filtration rate [GFR] of at least 40 mL/min/1.73 m2). The LVM index was estimated by indexing LVM to height(2.7). Sixteen patients had a cadaveric transplant and seven had a live donor transplant; the mean duration between the two studies was 1.9 +/- 1.6 yr; and the mean GFR was 55.0 +/- 21.4 mL/min/1.73 m2. There was no significant difference in the mean values of the LVM index while on dialysis and after renal Tx (43.9 +/- 17.8 g/m2.7 and 39.3 +/- 12.0 g/m2.7, respectively, p = 0.19), or in the prevalence of LVH (52% and 56%, respectively). Interval changes in the LVM index in individual subjects between the two studies were significantly associated with interval changes in indexed systolic (r = 0.42, p = 0.04) and diastolic (r = 0.42, p = 0.05) blood pressures. Interval changes in hemoglobin, blood urea nitrogen (BUN), creatinine, and duration after Tx did not correlate with changes in the LVM index. There was no significant difference in LVM index change according to the type of dialysis, donor source, and the cause of renal failure. In multivariate analysis, the baseline LVM index and changes in indexed SBP were independent predictors for LVM index change after renal Tx. We conclude that LVH persists in children and adolescents after renal Tx. Control of blood pressure might be an important factor in regression or prevention of progression of LVH in these patients.