The terpenes constitute one of the largest and most structurally varied groups of natural products, and they exhibit a tremendous diversity in chromatographic properties, both within and between the various classes. This chapter focuses on the chromatography of relevant higher and lower isoprenalogs. The terpenoid vitamins (A, E, and K) have each been dealt with separately. Phosphorylated terpenes and glycosylated terpenes are described as these derivatives exhibit profound chromatographic differences relative to their parent terpenyl moieties. The chromatographic isolation of mevalonic acid (or mevalonolactone) is often required in the preparation of this isotopically labeled substrate for studies on isoprenoid biosynthesis, and, in the assay of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG CoA reductase), a key regulatory enzyme of the isoprenoid pathway. The enzyme assay generally involves the separation of the product, mevalonic acid (as the derived lactone), from the substrate, HMG CoA (often determined as HMG). Several simple thin layer chromatography (TLC) methods have been devised for this purpose, including chromatography on silica gel with acetone-benzene (1:1) and other developing solvents, or on Super-Cel–CaSO4 (3:1) or cellulose.