The excretion and the metabolism of approved or illegal drugs can be investigated and monitored with several analytical techniques. We conduct excretion studies with volunteers and develop suitable analytical methods to determine excreted metabolites. My research focuses on beta-blockers, adrenergic beta-2 agonists, and steroids. The separation is performed via High-Performance Liquid Chromatography, Supercritical Fluid Chromatography, and gas Chromatography hyphenated to a triple quadrupole (Q) or a quadrupole-time-of-flight (QToF). I use experience enhanced with design-of-experiments-based data evaluation (DOE) to develop highly sensitive methods. A special focus in developing the methods is the investigation of matrix effects. Chiral chromatography (HPLC and SFC) allows for the stereoselective detection and quantitation of drugs and their metabolites and, thus, monitoring the stereoselective pharmacokinetics.