ROUTINE TOXICOLOGICAL ANALYSES ARE MORE EXHAUSTIVE THAN IN THE PAST, BUT IT IS DIFFICULT TO COMPARE THE PRESENT EXTENT OF DRUG ABUSE WITH THAT IN THE PAST. DRUG CLASSES INCLUDE VOLATILE AGENTS, SUCH AS ETHYL ALCOHOL, AND ORGANIC COMPOUNDS, WHICH ARE SUBDIVIDED INTO THREE TYPES: ACIDIC, NEUTRAL, AND BASIC. TECHNIQUES OF DRUG IDENTIFICATION INCLUDE COLOR TESTS, MICROCRYSTALLINE TESTS, ULTRAVIOLET SPECTROPHOTOMETRY, INFRARED SPECTROPHOTOMETRY, FLUORIMETRY, PHOSPHORIMETRY, MASS SPECTROMETRY, MASS FRAGMENTOGRAPHY, PAPER CHROMATOGRAPHY, THIN-LAYER CHROMATOGRAPHY, GAS-LIQUID CHROMATOGRAPHY, HIGH PRESSURE LIQUID CHROMATOGRAPHY, AND IMMUNOCHEMICAL METHODS. CONDUCTING A TOXICOLOGICAL ANALYSIS BEGINS WITH OBSERVING OR LEARNING THE SUBJECT'S SYMPTOMS, SUCH AS LETHARGY OR TREMORS, WHICH MAY SUGGEST THE PRESENCE OF SPECIFIC CHEMICALS OR DISEASES. CASE HISTORIES OF TOXICOLOGICAL INVESTIGATIONS ILLUSTRATE THE APPLICATION OF ROUTINE BIOCHEMICAL DATA AND OBSERVED SYMPTOMS IN DIAGNOSING POISONING. DIFFERENT ANALYTICAL TECHNIQUES ARE APPROPRIATE FOR DIFFERENT TYPES OF DRUGS. BECAUSE INNOCUOUS MATERIALS AND DRUGS OF ABUSE SHARE MANY SIMILAR CHARACTERISTICS, THE IDENTITY OF ANY SUSPECT SUBSTANCE SHOULD BE CONFIRMED BY USE OF THREE OR MORE ANALYTICAL TECHNIQUES. THE MOST IMPORTANT ROLE OF LABORATORIES DOING TOXICOLOGICAL EVALUATIONS IS MONITORING THERAPEUTIC USES OF DRUGS AND PREVENTING OVERT TOXIC REACTIONS. TABLES, EXTENSIVE FIGURES SHOWING DIFFERENT ANALYTICAL METHODS' RESULTS FOR VARIOUS DRUGS, A BIBLIOGRAPHY, AN INDEX, AND AN APPENDIX PRESENTING EXAMPLES OF ULTRAVIOLET ABSORPTION SPECTRA OF VARIOUS DRUGS, ARE INCLUDED. (CFW)