Toxicological tests of blood, urine and other specimens for drugs of abuse must meet the minimum standards accepted within the toxicology community. No conclusions as to presence of a drug, its concentration or its physiologic effects can be made if there is a failure to meet those standards. The article reviews the need for confirmation of immunoassay screening results and validation studies, minimum GC/MS standards for qualitative identification, limits of detection and quantitation, appropriateness of standards and controls and the correlation of quantitative results to impairment. It then presents four cases where certain of the procedures were not followed or did not meet minimum standards. Drug testing should reflect the needs of the case and must include confirmation. Testing should be targeted towards suspected drugs, while maintaining enough sample for confirmation of presumptive findings. The article proposes that an individual be presumed drug-free unless there is overwhelming scientific evidence to the contrary. Figure, tables, references