AIM:To investigate the toxicities,biodistribution andanticancer effect of 5-fluorouracil controlled release implant(5-FUCI) on Walker 256 carcinosarcoma cells in Wistar rats.METHODS:Experiment 1:Wistar rats were randomlydivided into three groups (27 rats per group).Blank implantwas implanted in left lobe of the liver,and rats were treatedwith saline solution (in group A) or 5-fluorouracil(subcutaneousinjection,group B).5-FUCI was inserted in left lobe of theliver (group C).The gastrointestinal and hematologicaltoxicities were observed and contents of element F in groupC were assayed.Experiment 2:on day 6 after Walker-256carcinosarcoma transplantation in left lobe of the liver,5-FUCI was implanted in right lobe of the liver (group E) orleft lobe (group F),and rats in control group (group D)were inserted blank implant.Tumor inhibition rate andsurvival time were investigated.RESULTS:5-FUCI showed no obvious toxic effect,extractionof Evan’s blue from gastrointestinal tissue was normal,theperipheral white blood cells and bone marrow nucleated cellswere not reduced,compared with control group (P>0.05).Histological examination revealed that there were no visiblechanges in small intestinal mucosa,The concentration of 5-fluorouracil in left lobe of the liver was 9.84,28,34 times asmuch as those of right lobe of the liver,heart and kidneyrespectively after the implantation in group C.They kept ahigh level of fluorouracil in left lobe of the liver,rangingfrom (4.414±0.482) % to (7.800±0.804) %,for eight weeks.Survival days were 28.0±2.2,30.0±3.2 and 38.7±6.7 d ingroup D,E and F,respectively.CONCLUSION: 5-FUCI shows no obvious toxicities to gastrointestinal tract and myelotoxicity. After implantation, it kept a high level of 5- fluorouracil in surrounding tissues of the implant for eight weeks. Its antitumor effect on Walker-256 carcinosarcoma is demonstrated. AIM: To investigate the toxicities, biodistribution and aticancer effect of 5-fluorouracil controlled release implant (5-FUCI) on Walker 256 carcinosarcoma cells in Wistar rats. METHODS: Experiment 1: Wistar rats were randomly divided into three groups (27 rats per group). Blank implant was implanted in left lobe of the liver, and rats were treated with saline solution (in group A) or 5-fluorouracil (subcutaneous injection, group B). 5-FUCI was inserted in left lobe of the liver (group C) .The gastrointestinal and hematologicaltoxic were observed and contents of element F in group C were assayed. Experiment 2: on day 6 after Walker-256 carcinosarcoma transplantation in left lobe of the liver, 5-FUCI was implanted in right lobe of the liver (group E) orleft lobe (group E) FULTS, 5-FUCI showed no obvious toxic effect, extraction of Evan’s blue from gastrointestinal tissue was normal, thep Eripheral white blood cells and bone marrow nucleated cells were not reduced, compared with control groups (P> 0.05). Histological examination revealed that there was no visible changes in small intestinal mucosa, The concentration of 5-fluorouracil in left lobe of the liver was 9.84, 28,34 times asmuch as those of right lobe of the liver, heart and kidneyrespectively after the implantation in group C. They kept ahigh level of fluorouracil in left lobe of the liver, rangingfrom (4.414 ± 0.482)% to (7.800 ± 0.804) %, for eight weeks. Survival days were 28.0 ± 2.2, 30.0 ± 3.2, and 38.7 ± 6.7 d.Endusion, it was.CONCLUSION: 5-FUCI shows no obvious toxicities to gastrointestinal tract and myelotoxicity. a high level of 5-fluorouracil in surrounding tissues of the implant for eight weeks. Its antitumor effect on Walker-256 carcinosarcoma is demonstrated.