Clinical pharmacology plays an important role in today's medicine. Due to the high sensitivity, selectivity, and affordability of a mass spectrometer (MS), the high performance liquid chromatography - mass spectrometry (LC-MS) analytical technique is widely used in the determination of drugs in human biological matrixes for clinical pharmacology. Specifically, LC-MS is used to analyze: anticancer drugs antidementia drugs antidepressant drugs antiepileptic drugs antifundal drug antimicrobial drugs antipsychotic drugs antiretroviral drugs anxiolytic/hypnotic drugs cardiac drugs drugs for addiction immunosuppressant drugs mood stabilizer drugs This book will primarily cover the various methods of validation for LC-MS techniques and applications used in modern clinical pharmacology.