The current discussion on "renewable resources", and the possibility of gene transfer into rapeseed, has led to many investigations into the biosynthetic pathways leading to industrially useful fatty acids. The various tribes and genera of the plant family Ranunculaceae contain a large variety of unusual fatty acids. Seed fatty acid patterns differ considerably from genus to genus and are chemotaxonomically significant indicators. Eranthis seed oil has now been found to contain a fatty acid pattern that deviates significantly from the eleven different fatty acid patterns that had been described in this plant family. The main fatty acid (up to 57%) is 13-cis, 16-cis-docosadienoic acid. Other, minor fatty acids found are delta 5-cismonoenoic, -dienoic, and -trienoic fatty acids that had already been reported to be constituents of the genus-specific seed oil fatty acid patterns of various genera from this plant family. Capillary gas-liquid chromatographic retention data indicate that 22:3 delta 5 cis, 13 cis, 16 cis is probably also present. Seed fatty acid chemotaxonomic evidence thus points to a different position of Eranthis within the tribes of this plant family. These findings again indicate that the plant family Ranunculaceae would be an ideal object to study fatty acid biosynthesis and phylogenetic evolution, because in other genera of this family other types of desaturation and chain elongation mechanisms predominate.