This chapter contains sections titled: Basics of Solid-Phase Extraction (SPE) Comparison to Other Technologies Uses of SPE SPE Formats SPE Apparatus Theory and Practice of SPE SPE Method Development SPE Phases An Example of SPE Method Development: The Isolation of N-Acyl Homoserine Lactones (AHLs) in Growth Media Special Topics in SPE Class-Specific SPE Cartridges Column Switching Protein Precipitation Versus SPE for Drugs in Biological Fluids Technologies Related to SPE Future Directions in SPE References