Early drug analysis involved various clinical methods based on urinalysis. Currently, drug testing is often performed in the laboratory or through onsite urinalysis methods. Almost all clinical laboratories involved in drug testing offer one or more of the following urinalysis techniques: gas chromatography/mass spectrometry, gas chromatography, thin layer chromatography, florescence polarization, enzyme immunoassay, radio immunoassay, and latex agglutination immunoassay. These methods all test for drug metabolites in urine. Technical issues associated with the effectiveness of urinalysis are addressed, including specificity, cross-reactivity, sensitivity, and cutoff levels. Strengths and weaknesses of laboratory versus onsite drug testing are discussed.