Mandatory drug testing in the United States was initiated by the Army in an effort to control illegal drug use in Vietnam. Subsequently, following the investigation of a plane crash of the aircraft carrier Nimitz in 1981, the Navy developed a similar program. In 1986, President Reagan issued an Excutive Order prohibiting use of illegal drugs by Federal employees. The Secretary of the Department of Health and Human Services was directed to formulate adequate regulations for urine drug testing and to accredit laboratories that could demonstrate their ability to fulfill these obligations. The National Institute for Drug Abuse (NIDA) was given this responsibility and has instituted a rigorous periodic proficiency testing and laboratory inspection program. As of November 1992, 91 laboratories were accredited by NIDA. Although only Federal employees were included in the original program, Federal agencies promulgated regulations in 1988 that required all contractors serving these agencies to insure that their workplaces and employees were drug free. Not to be overshadowed, private industry decided they should also be involved, and many companies developed drug testing programs. These private industry programs are not obliged to follow the NIDA program, but most do so. Some use drug testing laboratories accredited by CAP-AACC. The drug testing programs by private industry are subject to regulations in several but not all states. Additional drug testing programs involve the criminal justice programs (prisoners and probationers), drug rehabilitation program participants and the judicial system (pretrial evaluation, prisoners and probationers). Collectively these programs have led to a multi-million dollar drug testing industry and the expenditure of additional funds for treatment and prevention programs. Few objective data are available on the number of positive drug tests. The military feel that their program is a significant deterrent to drug use because less than 1% of those tested are found to be positive. In non-regulated private industry, pre-employment positive tests average 10%, but employees' positives average 1–2%. In the NIDA labs the average positive rate is 3%. The criminal justice system yields about a 10% positive rate by probationers and those in rehabilitation programs. The cost/benefit ratios of all these programs are seldom calculated. Until they are, it will be difficult to assess the ultimate value of these programs.