(FORTUNE Magazine) – As a good-will gesture, Irv Klein and Jonah Kaufman hired several mentally handicapped adults to work in their 13 McDonald's restaurants on Long Island, New York, last year. The experience was so successful they recruited 34 more. The franchise owners found the new hires to be reliable, hardworking individuals. With unskilled workers in dwindling supply, service companies are increasingly looking to the mentally retarded to man mops and grills. The fast-food industry, where the annual employee turnover rate is 200%, welcomes their loyalty. Of the 40 mentally handicapped adults hired by McDonald's on Long Island, only four have left. Says Kaufman: ''These people never come in late and are rarely sick.'' Kentucky Fried Chicken employs 28 mentally handicapped workers at company- owned restaurants in Virginia and is stepping up recruitment in Georgia and Kentucky. Flo Barber, a company human resources director, points out that these workers don't mind the chores that teenagers often find boring. Marriott Corp. has been hiring the mentally handicapped for over ten years; it currently employs about 1,000. Pam Farr, Marriott's director of human resource planning, says the productivity of retarded employees is the same as that for nondisabled workers. - C.G.