Data on the detection times of drugs of abuse are based on studies of controlled administration to volunteers or on the analysis of biologic samples of subjects who are forced to stop their (often chronic) use of drugs of abuse, eg, because of imprisonment or detoxification. The detection times depend mainly on the dose and sensitivity of the method used and also on the preparation and route of administration, the duration of use (acute or chronic), the matrix that is analyzed, the molecule or metabolite that is looked for, the pH and concentration of the matrix (urine, oral fluid), and the interindividual variation in metabolic and renal clearance. In general, the detection time is longest in hair, followed by urine, sweat, oral fluid, and blood. In blood or plasma, most drugs of abuse can be detected at the low nanogram per milliliter level for 1 or 2 days. In urine the detection time of a single dose is 1.5 to 4 days. In chronic users, drugs of abuse can be detected in urine for approximately 1 week after last use, and in extreme cases even longer in cocaine and cannabis users. In oral fluid, drugs of abuse can be detected for 5–48 hours at a low nanogram per milliliter level. The duration of detection of GHB is much shorter. After a single dose of 1 or 2 ng of flunitrazepam, the most sensitive methods can detect 7-aminoflunitrazepam for up to 4 weeks in urine.