Objective　To probe the curative effect of thiotepa and mitomycin C for the prevention of the relapse of pterygium after its operation.Methods　One hundred and eighty-two cases with pterygium were randomly divided into two groups:one group of thiotepa(158 cases with 169 eyes)and the other group of mitomycin C (24 cases with 24 eyes) and a comparative study was conducted.Thiotepa was used through dropping on the third day after the operation(1∶2 000),while MMC was used in the same way during the operation and on the third day after the operation respectively(0.2g*L-1).Results　In the group of thiotepa,the wounded skin on the cornea was repaired significantly more rapidly than that in the group of mitomycin C,and the rate of the relapse of pterygium was lower in the former group than that in the latter one.Conclusion　Applying thiotepa by dropping after the excision of pterygium is a safe,simple and effective supplementary measure for the prevention of pterygium relapse and also effective for recurring cases.