A HIV positive patient who received a cadaveric renal transplantation developed tacrolimus toxicity as manifest by renal failure and decreased consciousness. This was due to atazanavir and ritonavir therapy for her HIV inhibiting the CYP3A4 hepatic enzyme resulting in accumulation of tacrolimus. Her HIV treatment was switched to raltegravir which is metabolized by UGT1A1 which does not affect tacrolimus. Tacrolimus was then reintroduced, and follow-up at 1 year demonstrated successful immunosuppression and undetectable HIV viral loads.