Diterpenes are composed of C20 hydrocarbons and have a general molecular formula C20H32. Diterpenes are distributed widely in nature (particularly in plants) and are frequently present in the families of Labiatae, Verbenaceae, Celastraceae, Euphorbiaceae, Thymelaeaceae as well as many genera such as Rhododendron and Taxus. In addition to plants and fungi, diterpenes are also found in many marine and insect species. According to “The Combined Chemical Dictionary,” more than 10,000 diterpenoids of over 100 skeletons have been characterized with new diterpene-derived frameworks emerging at an accelerating speed. Due to modern spectroscopic techniques, diterpene related research has greatly advanced with many complicated structures determined successfully in a short amount of time. More importantly, in-depth bioactivity research has demonstrated that some diterpenoids are valuable for treating severe diseases. For example, taxol showed signiﬁcant cytotoxic and antileukemic actions. It was approved as an anticancer drug for treating ovarian, breast, lung and squamous cancers. Taxol has become one of the most prescribed cancer-treating medicines. Andrographolides, isolated from Andrographis paniculata, exhibited anti-inﬂammatory and anti-bacterial activities to permit applications for treating gastritis, enteritis and pneumonia. It is anticipated that the utilization of diterpene compounds in medicine is still at its early stage, as more promising bioactivities of diterpenes need to be explored. The main diterpene skeletons are illustrated below.