However, a number of special factors must be considered in drugs/driving toxicology, including limited access to subjects and specimen quantities, the need to fix time versus effect, the lack of information about tolerance and dependency, and the probability of court challenge. The leading analysis methods available in this area include chromatographic, spectrometric, and immunochemical techniques. Recent advances relevant to the problems of drugs/driving include developments in therapeutic drug monitoring, a proliferation of assays, expansion of noninvasive sampling methods, ready availability of drug and metabolite standards, increased automation and proficiency in toxicological analysis, and an expanded literature. These advances have resulted in greater sensitivity, improved selectivity and specificity, increased efficiency, and reduced costs of analysis. A number of new techniques hold great future promise in this area. These include atmospheric pressure ionization breath analysis, improved immunofluorescence and fluorescence techniques, and drug/metabolite ratio measurement. More research will be needed to resolve problems related to concentration/effect curves, habituation and tolerance phenomena, and other pharmacodynamic and pharmacokinetics aspects. 11 tables and 21 references.