Insulin resistance is common posttransplantation and contributes to both new onset diabetes after transplantation and the metabolic syndrome. Insulin resistance indexes have never been validated in transplant recipients on tacrolimus compared with cyclosporine, although it is more diabetogenic. We aimed to assess these indexes in renal transplant recipients on tacrolimus as primary immunosuppressant.Retrospective analysis of 76 frequently sampled, intravenous glucose tolerance tests (for insulin sensitivity) in 38 nondiabetic renal transplant recipients on tacrolimus-centered immunosuppression. Indexes tested were fasting glucose/insulin ratio, homeostasis model assessment (HOMA) index, 1/HOMA, log (HOMA), quantitative insulin sensitivity check index, and the McAuley's index. Indexes were also compared against waist/hip ratio and C-reactive protein (CRP). Multivariate linear regression analysis was performed to determine independent variables predictive for insulin resistance.Insulin sensitivity successfully correlated with all indexes: fasting glucose/insulin ratio (r=0.246, P=0.033), HOMA index (r=-0.240, P=0.038), 1/HOMA (r=0.282, P=0.014), log (HOMA) (r=-0.316, P=0.006), quantitative insulin sensitivity check index (r=0.320, P=0.005), and McAuley's index (r=0.323, P=0.005). McAuley's index also correlated strongest with waist/hip ratio (r=-0.425, P<0.001). All indexes failed to correlate with CRP. Variables independently associated with insulin sensitivity were HbA1c (r=0.189, P=0.019), pulse pressure (r=0.146, P=0.021), and CRP (r=0.210, P=0.010).Insulin resistance indexes are valid in transplant recipients taking tacrolimus, with McAuley's index the strongest surrogate.