AIM: To assess the effectiveness of immunosuppressants in the prophylaxis of corneal allograft rejection after high-risk keratoplasty and normal-risk keratoplasty. METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, CNKI, VIP and reference lists of articles. Date of most recent search: 18 June, 2011. All randomised controlled trials (RCTs) assessing the use of immunosupressants in the prevention of graft rejection, irrespective of publication language. Two authors assessed trial quality and extracted data independently. Only dichotomous outcomes (clear graft survival, ratio of immune reactions and side effects) were available and were expressed as relative risk (RR) and 95% confidence intervals (CI). RESULTS: Seven studies were included in this review. In the comparing of mycophenolate mofetil (MMF) with placebo, the results showed MMF could significantly reduce immune reactions compared with placebo (RR 1.08 95% Cl 0.95 to 1.21), but no effect on clear graft survival (RR 1.11 95% Cl 0.90 to 1.35). In clear graft survival and immune reactions, MMF and cyclosporine A (CsA) showed similar effect (RR 1.11 95% Cl 0.90 to 1.35, and RR 1.48, 95% Cl 0.56 to 3.93, respectively). Tacrolimus (FK506) and steroid showed similar effects on clear graft survival and immune reactions (RR 0.32, 95% CI 0.02 to 6.21, and RR 1.00, 95%CI 0.88 to 1.14, respectively). No drug relative side effect has been found. CONCLUSION: MMF may reduce immune reactions in both normal-risk and high-risk rejection of penetrating keratoplasty. CsA and FK506 showed similar effects as MMF. However, due to the lack of large clinical trials, the evidence remain weak, the quality of evidences were rated as very low to moderate. Large, properly randomised, placebo-controlled, double masked trials are needed to evaluate the effect of immunosuppressants.