A new monomer, exo-3,6-epoxy-1,2,3,6-tetrahydrophthalimidoethanoyl-5-fluorouracil (ETFU), was synthesized by the reaction of exo-3,6-epoxy-1,2,3,6-tetrahydrophthalimidoethanoyl chloride (ETPC) and 5-fluorouracil (5-FU). The homopolymer of ETFU and its copolymers with acrylic acid (AA) and vinyl acetate (VAc) were prepared vi a photopolymerizations with 2,2-dimethoxy-2-phenylacetophenone at 25 degreesC for 48 h. The structures of the synthesized monomer and polymers were identified by Fourier transform infrared, H-1 NMR, and C-13 NMR spectroscopy and elemental analysis. The ETFU contents in poly(ETFU-co-AA) and poly(ETFU-co-VAc) were 26 mol % and 26 mol %, respectively. The number-average molecular weights of the polymers, as determined by gel permeation chromatography, ranged from 5600 to 17,000. The in vitro cytotoxicities of 5-FU and the synthesized samples against mouse mammary carcinoma and human histiocytic lymphoma cancer cell lines increased in the following order: ETFU > 5-FU > poly(ETFU-co-AA) > poly(ETFU) > poly(ETFU-co-VAc). The in vivo antitumor activities of the polymers against Balb/C mice bearing the sarcoma 180 tumor cells were greater than those of 5-FU at all doses tested. The inhibitions of the samples for SV40 DNA replication and antiangiogenesis were much greater than the inhibition of the control.