Preheat oven to 350°F. In a large pot of boiling, salted water, cook ziti until just barely tender; drain and place in a large bowl.

Mix ricotta cheese and half the mozzarella cheese with the ziti. Coat a 9" x 13" baking pan with nonstick baking spray; cover bottom of pan with half the spaghetti sauce. Spoon ziti mixture into pan; cover with remaining spaghetti sauce. Sprinkle with Parmesan cheese and top with remaining mozzarella cheese.

Bake 20 to 30 minutes, or until cheese melts and is light golden.