Confirmed positive urines for marijuana showed a small but significant decline from about 1.2 percent confirmed positive among U.S. Navy recruits entering service school commands in 1984 to 0.9 percent among Navy service school members in 1988 and from 2.0 percent among U.S. Marine Corps recruits entering service schools in 1984 to 0.8 percent among Marine Corps service school members in 1988. Navy and Marine Corps recruits showed a significantly higher confirmed positive use rate (6.1 and 3.3 percent, respectively) compared to service school members, perhaps reflecting their recent civilian use pattern. The relatively high confirmed positive cocaine rate among all groups may have reflected an increasing trend in all populations confirming a similar trend in high school and other civilian populations. Generally, the frequency of confirmed positive urines with amphetamines and opiates, based upon the findings at the Navy Drug Screening Laboratory at Great Lakes, has been static except for an apparent recent increase in amphetamine use in 1988. The decline in confirmed positive drug urinalyses among service school members from both the Navy and Marine Corps indicated that perhaps education and maturity had a positive effect upon their behavior. (Author abstract)