had 2 episodes of CMV infection despite prophylactic Gancyclovir and 3 had recurrent respiratory tract infections), 5 experienced biopsy proven rejection and 3 pts were started on a CNI free protocol due to CNI side effects. The contribution of the Immuknow assay measurement was assessed. Results: Mean Immuknow levels were low in the infected pts (235) and high in the pts with rejection (575). During the change to CNI free protocol, mean Immuknow levels were appropriate (426). In the fungal infected pts, the immunosuppressive treatment was diminished to low doses of steroids, lower trough CNI levels, omitting mycophenolate moefetil. The lower Immuknow levels encouraged us to continue the low potency immunosuppression. In the CMV and the respiratory tract infected pts, the Immuknow levels were low despite CNI therapeutic drug levels. Their immunosuppressive regimen was changed to a less potent one. In the pts with rejection, steroids were added and MMF was changed to everolimus. The appropriate Immuknow levels during the change to the CNI free protocol reflect the uneventful protocol change. Conclusions: Monitoring the Immuknow levels is a valuable and simple tool for immunosuppressive therapy monitoring. It helps decision making in complex situations allowing therapeutic changes that can favorably affect the outcome of HTx recipients.