Cuphea is unique among all flowering plants for the diversity of medium chain fatty acids produced as dominant fatty acids in the seed oils. The genus is a focus of research as a renewable source of MCTs for use by the chemical, food and health industries and as a model organism for the elucidation of biosynthesis of fatty acids. Seed oil composition is reported in 15 taxa, including 13 species previously unstudied. Results mostly substantiate patterns established in earlier studies in which species emphasize production of a single fatty acid, either C8:0, C10:0, C12:0, C14:0 or C18:2. Three species are unusual in producing equal amounts of C8:0 and C10:0, C12:0 and C14:0, and C10:0-C12:0-C14:0, respectively. In C. pulcherrima, 94% of total seed oil composition is caprylic acid (C8:0) and in C. schumanni, 94% is capric acid (C10:0). These are the highest single fatty acid percentages reported in the genus. Representatives of sect. Ornithocuphea are analysed for the first time and new compositional seed oil patterns are reported in sections Brachyandra and Melvilla. © 1992.