(FORTUNE Magazine) – His normally ruddy face is covered with a red rash, a painless but disfiguring skin problem Roger Smith says his doctor attributes ''99% to stress.'' It is ! not hard to see why. After 38 years with General Motors, Smith is routinely putting in exhausting days. Recently he returned to Detroit from Washington at 2 A.M. only to leave again at 8 A.M. Running the world's biggest industrial company, he notes, is no fun right now. It seemed as if it would be at the start. Smith, 62, praised as a bold and visionary thinker shortly after taking over in 1981, has instigated more changes than anyone since the legendary Alfred Sloan, GM's chief from 1923 to 1946. Smith shook up GM by reorganizing its five car divisions into two, buying Hughes Aircraft and Ross Perot's Electronic Data Systems, creating the ''no-year'' Saturn car project, and injecting massive doses of technology into GM's factories. But getting some payoff from all those expansive plans has proved harder than Smith expected. GM's share of the U.S. market has sunk from 44% to 36% because of look-alike cars and sloppy assembly. Ford earned more money last year (see No. 4). Smith, meanwhile, has been drawn into a public fight with Perot, who criticized him for lack of leadership and acuity. Other critics call Smith ''Squeaky'' behind his back. A man of medium height and build, Smith has a somewhat highly pitched voice that speech lessons have failed to deepen. Always tenacious and lately defensive, Smith is fond of saying that he is not as smart as observers said several years ago, nor as dumb as they say now. ''You have to take the long- term view,'' he says. ''I feel more confident now that, except for sales, what we're doing is right.'' As evidence he cites new cars built with fewer worker hours, improving vehicle quality, and what he insists is GM's technological lead over both Ford and Chrysler. While conceding he underestimated the demands of the chairmanship, Smith still doggedly calls it ''the best job in the world.'' He grew up in Detroit, the first GM chairman in 71 years to do so, the son of an entrepreneur who started a small bank and then became controller of a metal fabricator. Smith nearly earned an engineering degree at the University of Michigan, but wound up majoring in business administration instead, adding an MBA at Ann Arbor in 1949.

He was headed for California and a job in the aviation industry, but his father persuaded him to try GM. Smith worked his way through various finance jobs, winning praise for his thoroughness and quick grasp of ideas. Accustomed to being in the driver's seat, Smith rides shotgun on weekends, ) while Barbara Ann, his wife of 33 years, steers the family car toward their second home on a small lake in northern Michigan. That is where Smith houses his collection of classic GM convertibles: a 1936 V-16 Cadillac with dual windshields, a 1960 Corvette, and a 1964 Corvair. Cars aside, Smith's true passion is for the outdoors. He and GM President F. James McDonald are among 20 owners of the Turtle Lake Club, a private 28,000- acre preserve in northern Michigan abounding in pheasant, turkey, and deer. Smith recently returned from an Alaskan fishing expedition with the youngest of his four children, Drew, who will enter Princeton in the fall. One of the drawbacks of Smith's job is that official duties tend to consume leisure time, even on trips he takes with his wife. But when he retires, Smith jokes, his wife will visit the GM plant and he will get to see Buckingham Palace.