PITTSBURGH — COLLEGE students increasingly want to live where their roommates don't use drugs or drink alcohol. Colleges and universities are beginning to listen and create substance-free housing. On some campuses, the results are spectacular. When University of Michigan officials kicked off substance-free housing in 1989, they set aside 500 dormitory spaces. Some 1,200 students applied. ''That told us we were on to something,'' recalls Alan Levy, director of public affairs for the university's campus housing. This fall, 2,600 of the 9,500 students living on campus have requested - and will get - rooms where the use of alcohol and drugs is forbidden. Other universities are just getting started. Following a task-force report on the subject, the University of Pittsburgh made its smallest dormitory substance-free for the school year. The move is symbolic, since the sororities in the building long ago banned drinking. But the university is looking at further steps. ''It's a doable situation, probably one that we're moving toward,'' says Jo Ann Woodson, director of the Office of Residence Life. Even fraternities and sororities are getting involved. The National Interfraternity Conference and the National Panhellenic Conference are organizing a task force that could begin substance-free pilot programs on selected campuses as early as January. ''We are seeing a rising number of people requesting substance-free living throughout the country,'' says Harriet Rodenberg, chairwoman of the Panhellenic Conference, which represents sororities on campuses around the country. Although sororities allow no alcohol or drugs, their help is key to changing behavior in fraternities. ''They really need our help in saying: You can have fun without alcohol,'' Ms. Rodenberg says. The biggest problem, by far, is drinking. When the University of Michigan surveys college students in its annual Monitoring the Future study, it has consistently found that nearly 9 out of 10 admit to drinking alcohol within the last year. That's far more than the 3 out of 10 students who used illicit drugs (mostly marijuana) or the 4 out of 10 who smoked cigarettes. There are some signs that the number of people drinking has fallen somewhat. In 1993, the latest figures available, the Michigan study found 72 percent of college students had used alcohol, down from 80.3 percent a decade earlier. But the challenge remains daunting. Technically, state laws make all underage drinking illegal. ''There are buildings that should be [alcohol-free], but there are people who do not abide by the laws of the state,'' says Ms. Woodson at the University of Pittsburgh. ''The culture is still resistant,'' adds Mr. Levy at the University of Michigan. If students who abuse alcohol merely get a slap on the wrist, the ban in residence halls won't have much impact. In fact, for all the progress the university has made in providing substance-free dorms, ''we see no particular decline in consumption patterns,'' he adds. A few alcohol-free programs have been dismantled for lack of interest. Montana State University has seen little or no growth in the number of students requesting substance-free living quarters for several years. The University of Connecticut's program, started five years ago, still has only 38 students who live in a designated substance-free environment, out of an undergraduate on-campus population of some 7,000. ''Frequently people see this as the answer to the alcohol,'' says Tim Foster, director of residence life at Carnegie Mellon University here in Pittsburgh. But colleges and universities have to do much more to reduce substance abuse on campus, he adds. Carnegie Mellon does not offer substance-free living, but emphasizes counseling and alcohol-education programs instead. There is also a danger of going too far in cracking down on substance abuse, Mr. Foster says. ''We do respect privacy rights of individual rooms.'' Students living at the new substance-free dormitory at the University of Pittsburgh are skeptical that alcohol use will diminish. Students who want to drink can still go to bars, says senior Kristy Drenocky. ''I don't see it as a problem,'' adds Sharon Harden, a sophomore. ''I think it's part of any college.'' Real changes in college behavior will depend on larger social trends, these university officials agree. Many of the successful substance-free programs on campus have been linked to broader programs aimed at better living. ''We do have a growing group of people who prefer to have healthier environments,'' says Bill Hettler, director of the health service at the University of Wisconsin at Stevens Point and cofounder of the National Wellness Institute. The university is considered one of the leaders in promoting healthy living on campus, including substance-free housing. ''The country has been moving toward more recognition that what we do is important and makes a greater impact [on health] than what doctors do.''