It is the practice of many pediatric renal transplant programs to 'convert' children taking cyclosporin A (CsA) to tacrolimus, although the indications for, outcome, and complications of this practice remain obscure. To better understand these aspects of tacrolimus 'conversion', a fax survey was sent to 119 North American pediatric renal transplant centers. Analyzable responses were received from 52 centers (44%), and included data from approximately 1,815 pediatric renal transplants performed between 1991 and 98. Strong indications for tacrolimus conversion were: antibody-resistant rejection, CsA-resistant rejection, and CsA intolerance (strong indication in 72%, 65%, and 52% of centers, respectively). Steroid-resistant rejection and cosmetic side-effects were considered strong indications less often. Initial anti-rejection therapy was usually increased corticosteroid dose (47/52 centers). Antibody therapy was most commonly used for steroid-resistant rejection (44 centers). For steroid- and antibody-resistant rejection, tacrolimus conversion was most common (33 centers). Tacrolimus conversion for antibody-resistant rejection led to improvement of serum creatinine (SCr) in 27% of patients, stabilization of SCr in 46%, worsening of SCr in 11%, and graft loss in 16%. Reported complications after tacrolimus conversion included hyperglycemia, hyperkalemia, lymphoproliferative disorder, infection, and neurologic problems. We conclude that the major indication for tacrolimus conversion in pediatric transplant programs appears to be rejection. Outcome after tacrolimus conversion appears good, with the majority of patients experiencing stable or improved allograft function. These data provide direction for further study, including timing of tacrolimus conversion and interaction with other therapies.