Composite heterophase organic-inorganic hybrid cryogels of poly(vinyl alcohol) (PVA) containing silica constituents were prepared and studied. Such constituents were formed in the course of hydrolytic polycondensation (sol-gel process) of tetra me th oxysilane (TMOS) introduced in to the aqueous polymer solution prior to its freeze-thaw treatment. It was shown that moderate (over the range of -15 to -30 degrees C) freezing, then frozen storage, and subsequent thawing of the water/PVA/TMOS systems resulted in the formation of macroporous composite cryogels filled with dispersed silica particles (discrete phase). The continuous phase of such gel materials represents the supramolecuJar PVA network, which is supposed to be additionally cured with the silicon-containing oligomeric cross agents formed from TMOS in the course of hydrolytic polycondensation. The incorporated silica components influenced the morphology of cryogels. The effects of significant increase in gel strength and heat resistance with increasing TMOS concentration in the initial feed and with thawing rate decreasing have also been observed. (C) 2007 Wiley Periodicals, Inc.