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 glomerular filtration rate (GFR) >50 ml/min/1.73 m2