The article first describes urinalysis screening tests, including enzyme immunoassay (EIA) and radioimmunoassay (RIA), the most frequently used screening techniques, and thin-layer chromatography. A confirmatory test of a positive screen should be a routine procedure for any employee drug testing program. The article describes the standard confirmation testing procedure, gas chromatography coupled with mass spectrometry (GS/MS). In addition to urinalysis, the article describes a second screening procedure for drugs, such as hair analysis. Hair analysis, in contrast to urinalysis, can determine the time frame in which a particular drug was used. It also avoids the privacy issues associated with the taking of urine specimens. Disadvantages of hair analysis are that it identifies only five classes of drugs, and it is costly. The article also discusses quality assurance in drug testing; measurement of drug quantity; cross-reactivity among drugs; detection time; the steady-state level; and answers for some defenses used by employees who test positive for drugs, such as the passive inhalation of marijuana smoke and accidental oral ingestion.