Background: Growth hormone (GH) is used to treat growth failure in children with GH deficiency. The safety and efficacy of GH after pediatric cardiac transplantation is not known. The objective of this study was to evaluate growth and cardiovascular effects of GH in children with growth failure after cardiac transplantation. Methods: Pediatric cardiac transplant recipients who received GH from 1994 to 2004 were evaluated. Growth, cardiac function, hemodynamics and rejection frequency were serially monitored for 2 years before, during and after GH. Eight age-matched heart transplant recipients undergoing a natural growth spurt were evaluated as controls. Results: The mean age of subjects at initiation of GH was 13 ± 3 years (mean duration 2.5 ± 1 years, n = 10), of whom 3 were GH-deficient. Growth velocity (GV) increased from 2.5 ± 2 to 8.6 ± 3 cm/year with GH. There was an increase in left ventricular (LV) shortening fraction (SF; 37 ± 1% to 41 ± 1%), LV mass (93 ± 11 to 118 ± 15 g/m2), LV volume (138 ± 14 to 188 ± 21 ml/m2) and cardiac index (3.1 ± 0.7 to 4.1 ± 0.5 liters/min/m2) during GH therapy (p < 0.05). After discontinuation of GH, SF, cardiac index and LV mass returned to normal, but LV volume did not. In control patients, LV volume increased without an increase in SF or mass. Rejection frequency did not change in either group. There were no adverse events related to GH. Conclusions: GH is safe and effective in treating growth failure in children after cardiac transplantation. GH therapy is associated with an increase in LV mass, volume and cardiac output. These changes are partially reversible after discontinuation of GH. The mechanisms and long-term consequences of these changes require further investigation.