Abstract: The in vitro release behavior, in vivo biodistribution and antitumor activity of N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer-5-fluorouracil conjugates (P-FU) were studied. The in vitro release behavior was evaluated by determining the amount of 5-fluorouracil (5-FU) released from P-FU in mice plasma at 37 ℃. The in vivo biodistribution and therapeutic evaluation were investigated with Kunming mice bearing hepatoma 22 (H22). The in vitro half-life (t_1/2) of P-FU in mice plasma was 32.4 h. It appeared that the circulation life time of the conjugates were 166 times longer than that of 5-FU. The AUC and t_1/2 of P-FU in tumor were 3.3 times and 2.3 times more than those of 5-FU, respectively. Therapeutic evaluation also demonstrated that the treatment with P-FU displayed stronger inhibition of the tumor growth when compared with that of 5-FU (P<0.05). HPMA copolymer is a potential carrier for 5-FU for effective treatment of cancer.