Poly(exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride)s [poly(ETA)s] and poly($alpha$-ethoxy-exo-3,6-epoxy-1,2,3,6-tetrahydrophthaloyl-5-fluorouracil)s [poly(EETFU)s ] with various average molecular weights were prepared by photopolymerizations. The number average molecular weights of the fractionated poly(ETA)s and poly(EETFU)s determined by GPC were in the range of 3,600∼21,000 and 3,600-33,400, respectively. The release rate of 5-FU from poly(EETFU) decreased with increasing average molecular weight. The in vitro cytotoxicity of poly(ETA) against a normal cell line was lower than that of 5-fluorouracil(5-FU), The in vivo antitumor activities of the synthesized samples at dosage of 0.8 mg/kg against mice bearing sarcoma 180 tumor cell line decreased in the following order: poly(EETFU) > poly(ETA) > EETFU > ETA > 5-FU. The antiangiogenic activities of the poly(ETA)s were better than those of 5-FU.