Extensive surveys of the fatty acid composition of seed oils from different species of higher plants have resulted in the identification of more than 210 naturally occurring fatty acids which can be broadly classified into 1 of 18 structural classes (Table 1). The classes are defined by the number and arrangement of double or triple bonds and various functional groups, such as hydroxyls, ketones, epoxys, cyclopentenyl or cyclopropyl groups, furans, or halogens. This level of structural diversity is similar to that of some of the least diverse families of plant secondary metabolites, a class of compounds which have been estimated to contain as many as 100,000 different structures. 3 A summary of the range of structures to be found in plant fatty acids and a small number of examples of representative fatty acids are presented in Table 2. Extensive lists of the amounts and sources of plant fatty acids are available in earlier reviews. 1,2,7-11 Because of the magnitude of this extensive and scattered literature which can no longer be adequately represented by traditional compilations, the development of a computer database of the fatty acid composition of all characterized plant species would be very desirable.