This dissertation is composed of two sections. The first section is concerned with the development and validation of stability indicating high performance liquid chromatography (HPLC) methods for the analysis of selected pharmaceuticals in intravenous fluid mixtures. The second section focuses on the development and validation of bioanalytical HPLC methods for the determination of selected pharmaceuticals in human plasma. Part I contains two chapters. In Chapter 2 four stability indicating HPLC methods were developed for the assay of the carbapenem antibiotic meropenem in combination with dopamine, aminophylline, metoclopramide or ranitidine in intravenous fluid mixtures. In Chapter 3 five stability indicating HPLC methods were developed for the assay of the protease inhibitor zidovudine (AZT) in combination with ceftazidime, chlordiazepoxide, dobutamine, lorazepam or ranitidine in intravenous fluid mixtures. UV detection was used for all of the separations. Accelerated stability studies were carried out on each drug by exposure to several different stressors for different time periods. The degraded drugs were then analyzed using the developed methods with a photodiode-array (PDA) detector and Waters Millennium32 PDA software to verify that degradation products did not interfere with the quantitation of each drug. In chapter 4 solid phase extraction and HPLC with UV detection was used to determine AZT and levofloxacin in human plasma. In chapter 5 high speed HPLC methods utilizing solid phase extraction and a new monolithic silica column were developed for the determination of drugs of abuse in human plasma.