Cook the macaroni according to package directions. Meanwhile, in a large saucepan, melt butter over medium-low heat. Add the flour, salt and pepper; stir until smooth; gradually add milk. Bring to a boil; cook and stir for 2 minutes or until thickened. Remove from the heat; stir in cheese until melted.
Drain macaroni. Add to the cheese mixture; toss to coat.