Methods that have been used by other investigators studying effects of occupational pesticide exposure were reviewed. Biological tests for intact pesticides and their metabolites are used primarily in research settings to establish patterns of absorption, metabolism, and excretion for specific compounds; to derive exposure limits, including permissible exposure levels (PELs) and field reentry intervals; and to evaluate the adequacy of these limits and of work practices and protective equipment. Whenever possible, use of a particular analysis in field studies has been documented, giving an indication of the flexibility of that method. Certain methods, notably those for detecting metabolites from exposure to organophosphorous insecticides, have been validated in terms of dose response relationships, allowing the assessment of biological effects from metabolite residues in blood or urine samples. Gas chromatography is now being replaced by liquid chromatography for measurement of many water soluble or solvent soluble biological molecules because this eliminates the need to convert the compound into volatile derivatives for gas partitioning. Organophosphate compounds, carbamates and metabolites, organochlorines, chlorophenols and nitrophenols, phenoxy herbicides, chlorinated- aniline metabolites, paraquat (4685147), and dithiocarbamates were discussed. Biological tests for intact pesticides and their metabolites have had little use in the routine biological surveillance of occupationally exposed workers in agriculture. Exceptions include biological monitoring of workers exposed to pentachlorophenol (87865), methyl-bromide (74839), and chlordimeform (6164983). Methods reviewed are of increasing importance in field investigations. Interpretation of this information is made more difficult by the fact that biological thresholds for most agricultural chemicals have not been established by national agencies for effects other than acute illness. Research is needed on the biological indices of exposure associated with adverse health effects in occupational exposure to pesticides, particularly for neurologic, carcinogenic, and reproductive effects.