(FORTUNE Magazine) – As concern over drug abuse has grown, so has the call to test U.S. government and private workers for drugs. While sports associations and government agencies have led the cry for drug testing, more corporations, fearing drugs' effects on worker productivity, are turning to tests either as a screen for job applicants or a deterrent for employees. According to the National Institute of Drug Abuse, nearly 30% of FORTUNE 500 corporations test employees' and applicants' urine for illegal drugs, up from 25% last year. Concern over drug abuse in the workplace is greatest on Wall Street, where big salaries and high pressure are perfect companions to drug addiction. Several brokerage firms test new employees for illegal drugs, including Salomon Brothers and Bear Stearns. The most aggressive, however, is Kidder Peabody, which has been testing job applicants since January and began testing employees in August. ''We are striving for a drug-free workplace,'' says Edwin A. Weihenmayer, vice president and director of human resources at Kidder. Weihenmayer says that a very small number of employees have tested positive for drugs. Users must enroll in a company drug-counseling program, break their addictions themselves, or look for a new job. Pharmaceutical companies manufacturing the chemical tests that detect illegal drugs, such as cocaine, marijuana, and opium, include Hoffmann-La Roche and Abbott Laboratories. Abbott executives say the market for the tests totals about $100 million a year and could reach $220 million by 1991. The tests involve reagents that when mixed with urine samples cause a chemical reaction to drugs that may be present. While the tests cost only a few dollars per sample, the equipment that measures the samples can cost more than $50,000. Most test kits are sold to independent labs, but they are simple enough for use in a company's medical department. Indeed, one kit called Aware is being marketed to parents for home use by American Drug Screens of Dallas, though urine samples must be sent to the company. About the only barrier to drug testing is critics who say it is unreliable and violates civil liberties. Test manufacturers say that their products' reliability has greatly improved. And a recent New York Times /CBS News poll showed that 72% of full-time workers surveyed said they would be willing to submit to voluntary drug tests at work. Of course, the volunteers aren't the ones with the problem.