Grease 9 x 9 x 2-inch baking pan.
In 2-quart saucepan stir together condensed milk, peanut butter, corn syrup and salt.
Cook over low heat, stirring frequently, 15 minutes or until thick.
Gradually add confectioners' sugar, stirring until blended. (If mixture becomes too stiff, knead with hands.) Press into prepared pan.
Refrigerate several hours or until firm.
Cut into 1-inch squares.
Store in tightly covered container in refrigerator.