Three types of poly(ethylene oxide) (PEO) networks cross-linked by silicone-based compounds have been formed. One type of network prepared from allyl-substituted poly(ethylene glycol) (PEG), is stable whereas the other two are degradable. The degree of swelling of the resulting hydrogels depends strongly on the PEO/silicone ratio and on temperature. From the weight fraction of soluble material in the networks, the extent: of cross-linking reaction has been estimated. The molecular weight between cross-links has been calculated independently from the weight fraction of soluble material in the networks and from swelling data.