Hydron, a hydrophilic polymeric hydrogel, has been shown to absorb and elute fluorouracil at predetermined rates in vitro. Fluorouracil-charged Hydron pledgets were found to significantly suppress Ehrlich's ascites tumor in CF1 mice compared with controls receiving nonmedicated implants of polymer. An implantable chamber was designed to provide sustained selective release of fluorouracil. Preliminary studies showed the unit was able to deliver high concentrations of the antitumor agent locally while completely sparing tissues remote from the implant site.