alpha -Methoxy-3,6-endo-methylene-1,2,3,6-tetrahydrophthaloyl-5-fluorouracil (MMTFU). was synthesized from 5-fluorouracil (5-FU) and alpha -methoxy-3,6-endo-methylene-1,2,3,6-tetrahydrophthaloylchloride (MMTC). Poly(3,6-endo-methylene-1,2,3,6-tetrahydrophthalicanhydride) [poly(MTA)] and poly(alpha -methoxy-3,6-endo-methylene-1,2,3,6-tetrahydrophthaloyl-5-fluorouracil) [poly(MMTFU)] were prepared from corresponding monomers by photo-polymerizations using 2,2-dimethoxy-2-phenylacetophenone as the photoinitiator. The synthesized MMTFU and polymers were identified by FT-IR, H-1-NMR, and C-13-NMR spectroscopies. The number average molecular weights and polydispersity indices determined by GPC were 6,200 and 1.3 for poly(MTA) and 7,700 and 2.9 for poly(MMTFU). The cytotoxicities of the prepared polymers were lower than that of 5-FU. The in vivo antitumor activities of the polymers against mice bearing sarcoma 180 tumor cell line were greater as compared with that of 5-FU. The antiangiogenic activity of poly(MTA) examined by the embryo chorioallantoic membrane assay was better than that of MTA.