Combine sugar, corn syrup and water in 3-qt. heavy saucepan. Cook over medium heat, stirring constantly until sugar dissolves. If sugar crystals form on sides of pan, wipe them off. Continue cooking to the hard ball stage (252°).
Meanwhile, beat egg whites until stiff, but not dry; blend in gelatin.
When syrup reaches 252°, pour in a thin stream over egg whites, beating constantly with electric mixer on medium speed. Beat as long as possible, using wooden spoon if mixture becomes too stiff for mixer.
Add nuts and pour into lightly buttered 9" square pan. When cool and firm, cut in 36 pieces.