The release of heparin from monolithic devices composed of different ratios of polyethylene oxide(PEO MW 20,000) and polydimethylsiloxane was investigated. Water soluble PEO plended into the polydimethylsiloxane proved a controlled release of heparin. The release rate of heparin could be controlled by varying the content of PEO and loading dose of heparin. The release rate of heparin from the devices increased as the content of PEO and heparin in the devices increased. The release rate of heparin from devices were related to nature of solute(ionic strength) and temperature. The release mechanism may be associated with the creation of pore or domine through the devices the water-uptake and the change in the physical structure of the polydimethysiloxane network.