Liquid chromatography (LC) is a separation method that is often used in clinical and pharmaceutical analysis, including in liquid chromatography–mass spectrometry. In this method, a sample is applied in the presence of a liquid mobile phase to a column that contains a support and a stationary phase. The general description of a separation in LC is discussed in this chapter, including ways of characterizing compound retention, peak-broadening, and the extent of peak separation. Mobile phases, elution methods, and stationary phases that are utilized in this technique are also described. This includes a discussion of LC methods based on partitioning (e.g., reversed-phase liquid chromatography and hydrophilic interaction liquid chromatography, or HILIC), ion-exchange (e.g., cation-exchange and anion-exchange chromatography), and size-exclusion. Other methods, such as adsorption chromatography and affinity chromatography, are examined as well. In addition, the instrumentation, columns, supports, and detectors that can be employed in LC are described.