There are basically two types of preparative liquid chromatography (PLC). One is low-pressure (typically under 5 bar) traditional PLC, based on the use of glass or plastic columns filled with rather low efficiency packing materials of large particles and large size distributions. A more recent form of PLC, high-performance PLC (HPPLC), has been gaining popularity over the past few years, particularly in the pharmaceutical industry. This type of chromatography makes use of stainless steel columns able to work at medium/high pressure (1000 to 1500 psi) and packed with medium/small-size particles (10 to 30 μm). HPPLC is closer to analytical HPLC (except for the size of the equipment) than to traditional PLC. Although both types of PLC have their specific fields of application, HPPLC is slowly replacing traditional PLC, particularly at the pilot and medium-size production levels. HPPLC, because of its higher column efficiencies and faster solvent velocities, permits more difficult separations to be conducted more quickly. This is very important in the pharmaceutical industry of today because new products have to be introduced to the market as quickly as possible. Having a powerful purification technique available makes it possible to spend less time on the synthesis conditions.