Quantitation of low concentration of drugs, metabolites and endogenous compounds in plasma has always been a difficulty and challenge task for analytical chemists in biomedical and pharmaceutical analysis. It often requires extracting and concentrating the analytes in the samples for quantitative analysis. Extraction from the plasma matrix potentially enables the simultaneous removal of endogenous interfering substances and the enrichment of the analytes. However, extraction procedures are frequently the most time consuming steps of the analytical process. Lack of robustness of the extraction procedure is a common problem leading to the invalidation of entire analytic runs. Solid- Phase Extraction (SPE) is a powerful sample preparation technique currently available for rapid clean-up and enrichment of sample analytes preceding chromatographic analysis. Compared to traditional liquid-liquid extraction (LLE), SPE provides major advantages in terms of simplicity, high throughput, robustness, and in most cases, greater cost effectiveness. A wide range of SPE resin chemistries is now available for various applications. The sampling format has also extended from simple packed disposable syringes to cartridges, disks, SPE pipette tips, 96-well and 384-well microplates. Therefore, SPE sample preparation techniques provide improved assay standardisation and hence better reproducibility. The objective of this article was to review literatures regarding SPE extraction theory, extraction modes and its application in clinical and pharmaceutical analysis. Updated information about the most important features of the SPE materials and the future trends in SPE sample preparation are also discussed.