Abstract: Cross-linked hydrophilic polymers, useful inter alia for the manufacture of contact lenses capable of absorbing water to a water content of 63 to 90% by weight while retaining excellent tensile strength contain hydrophilic units of N-vinyl-2-pyrrolidone, with optionally other hydrophilic monomers in minor amount, hydrophobic units of cycloalkyl acrylate, methacrylate or itaconate, and optionally other hydrophobic monomers, and units of a cross-linking agent. They may be made by polymerizing the monomers in the presence of a free radical generating catalyst. The polymer may then be shaped and hydrated.