The armed forces have long recognized a legitimate public interest in a drug-free military that overrides individual rights to privacy and withstands constitutional scrutiny. Mandatory urinalysis testing has become an established procedure in the military. Six categories of urinalysis tests are conducted in the armed forces: search and seizure with a warrant when there is probable cause to believe a service member has ingested drugs or has committed a drug-related offense; health and welfare inspections that include unit sweeps and random sampling of an entire military group; tests for valid medical reasons; and commander-directed tests ordered when there is a reasonable suspicion of illegal drug involvement; and in the course of an accident investigation. The successful prosecution of cases that involve a positive urinalysis test is based on proof of chain-of- custody of the urine sample and proof of scientific reliability of the laboratory analysis. Data on drug-use rates for marijuana and cocaine among military personnel show that the prevalence of drug abuse decreases with the onset and continuation of drug testing. 2 figures