The chapter discusses the basics of inductively coupled plasma mass spectrometry (ICP MS) detection in high-performance liquid chromatography (HPLC), especially in terms of interfacing it with capillary and nanoHPLC, and overviews the application areas. The ICP MS torch operates at the atmospheric pressure. The ions formed must then be introduced into the mass spectrometer via the interface cones. Mass analyzers typically employed for the separation of ions generated in an ICP typically include quadrupole, time-of-flight, and sector-field instruments. The most popular mass analyzer, a quadrupole mass filter consists of four parallel metal rods arranged in a way that two opposite rods have an applied potential of (U + V cos(ωt)) and the other two rods have potential of -(U + V cos(ωt)), where U is a dc voltage and V cos(ωt) is an ac voltage. Reversed-phase HPLC is the preferred separation technique for weakly polar compounds in application areas such as peptide mapping, and amino acid, phospholipid, and protein separations.