A golf ball comprising a single-layer core having a diameter of 0.10 inches to 1.50 inches, a PGA compression of 110 or less and, and comprising a copolymer of ethylene and an .alpha.,.beta.-unsaturated carboxylic acid, the acid being 100% neutralized by a salt of an organic acid, a cation source, or a suitable base of the organic acid; and a thermoplastic or thermoset cover comprising polyurethane, polyurea, epoxy resins, polyamides, polyesters, polycarbonates, or a copolymer comprising urethane and urea segments.