Because cystinotic patients are polyuric and may have severe proteinuria, each of which is a potential risk factor for graft thrombosis, preemptive transplantation for them is questionable. The objectives of this study were to characterize the changes in urine volume and protein excretion at various stages of cystinosis, determine whether there is serologic evidence of hypercoagulability, and review the clinical experience in renal transplantation in cystinotic children. The records of cystinotic patients followed at the Montreal Children's Hospital between 1992 and 1998 were reviewed. Urinary volume, protein excretion, and coagulation markers were collected to determine the glomerular filtration rate (GFR) >50 ml/min/1.73 m2, <20 ml/min/1.73 m2, before and after starting dialysis. In addition, graft failure and graft thrombosis rates were obtained from the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) database. Urinary volume and protein excretion remained elevated throughout different phases of the disease. Coagulation factors were within normal limits for all patients. In the NAPRTCS database there were four thromboses among the 114 patients transplanted cystinotic patients. All these occurred in cadaveric grafts and only one occurred after preemptive transplantation. Despite polyuria and severe proteinuria, children with cystinosis do not appear to be at an increased risk of graft failure or graft thrombosis.