An 11-year-old girl, who was a renal transplant recipient, developed linear growth failure associated in time with sirolimus (SRL) treatment. After 5 years of functional graft [creatinine clearance (CCr) 90 ml/min per 1.73 m(2) body surface area], she developed acute renal failure due to calcineurin inhibitor-related hemolytic uremic syndrome, and cyclosporine A was replaced by SRL. Before the drug change, she had been growing normally (5.5 cm/year) and had reached the 33.9 percentile (P) of height (z-height -0.41), similar to her target. Two years later, her height had decreased to P 6th (z-height -1.54), as her growth velocity had diminished to 2.2 cm/year, despite optimal renal function (CCr 68 ml/min per 1.73 m(2)). Human recombinant growth hormone was needed to promote her catch-up growth and achieve the P 49th of height (z-height -0.03). SRL may have deleterious effects on growing children due its characteristic anti-proliferative and anti-angiogenic properties. Pediatric transplant recipients' linear growth should be cautiously monitored while they are being given SRL.