Present article reviews about clinical pharmacology of mycophenolic acid (MPA), the active form of mycophenolate mofetil (MMF), as widely used component of immunosuppressive regimens in the organ transplantation field. MMF, used alone or concomitantly with cyclosporine or tacrolimus, has approved in reducing the incidence of acute rejection and has gained widespread use in solid organ such as kidney, heart and liver transplantation. The application of MPA and development of MMF has shown a considerable impact on immunosuppressive therapy for organ transplantation as a new immunosuppressive agent with different mechanism of action from other drugs after early 1990s. In particular aspect, use of MMF, a morpholinoethyl ester of MPA, represented a significant advance in the prevention of organ allograft rejection as well as allograft and patient survival. In considering MMF clinical data, it is important to note that there is a strong correlation between high MPA area under curve(AUC) values and a low probability of acute allograft rejection. Individual trials have shown that MMF is generally well tolerated and revealed that MMF decreased the relative risk of developing chronic allograft rejection compared with azathioprine. Recent clinical investigations suggested that improved effectiveness and tolerability will results from the incorporation of MPA therapeutic drug monitoring into routine clinical practice, providing effective MMF dose individualization in renal and heart transplant patients. Therefore, MMF has a selective immunosuppressive effect with minimal toxicity and has shown to be more effective that other agents as next step of immunosuppressive agents and regimens that deliver effective graft protection and immunosuppression along with a more favorable side effect.