The average pore size value of gels containing polyacrylamide, covalently linked to agarose, was found to be 30% higher than the value of a regular N,N'-methylenebisacrylamide (Bis) cross-linked gel of the same %T. By increasing the agarose concentration (10% of the total amount of polyacrylamide), gels containing low amounts of acrylamide (1.5-2%) are reproducibly obtained; their pore sizes are 130% larger than the pore sizes of a 4%T, 3.3%C polyacrylamide gel. In general, mixed-bed matrices were found to be more elastic and mechanically stronger than classical polyacrylamide gels since an agarose-induced gelation process takes place during their polymerization.