Heat pita breads in preheated oven for about 5 minutes, or until slightly browned.
Meanwhile, in a large bowl combine the chicken, lettuce, onion, cheese, mayonnaise, ketchup, chili sauce, hot pepper sauce, lemon juice and ground black pepper. Mix well. (Note: If making this for kids, you may want to exclude chili sauce and hot pepper sauce.)
Slice hot pita breads around the edges to form pockets; fill bread pockets with chicken mixture. Serve hot.