This invention pertains to a polymeric composition and an antimicrobial composition, each comprising a superabsorbent polymer (SAP), such as used in diapers and sanitary napkins, and peroxide. The superabsorbent material can be made by the process of treating a preformed SAP, such as a crosslinked polyacrylate salt, with a treatment solution comprising hydrogen peroxide dissolved in water, followed by drying. The resulting superabsorbent material has strong antimicrobial activity. Optionally, the treatment solution may also contain a metal salt, including those of zinc, zirconium, and magnesium.