Analytical approaches to the determination of pesticides and metabolites in human and animal tissues will take many forms. Several factors must be considered in choosing an analytical scheme if the results are to be meaningful. Whenever possible the residue chemist will use standardized methodology which has been subjected to evaluation by collaborative studies. In the absence of such methods, the analyst must be aware of the capabilities and limitations of the various steps in the analytical procedure of choice. Extraction and cleanup efficiency must be considered in view of the determinative method to be used. Highly efficient gas chromatographic columns coupled with sensitive and selective detector systems are powerful analytical tools. One must be cautious, however, when relying on gas chromatographic peak retention time for compound identification. For a complete analysis, confirmatory techniques should be used. The available sample size may dictate the use of a micro method of analysis and, at the same time, preclude certain confirmatory techniques. Advantages of micro methods include speed, smaller glassware and minimum solvent volumes.