AbstractThe oils from sclerotia or from suitable mycelial cultures ofClaviceps purpurea (ergot) contain up to 44% of ricinoleic acid but no free hydroxyl groups. This is due to the presence of, besides normal triglycerides, tetra‐acid, penta‐acid and hexa‐acid triglycerides. These contain respectively one, two and three ricinoleic acids esterified to glycerol, these in turn being acylated at their hydroxy groups with normal long‐chain fatty acids. By suitable complementary use of TLC, GLC and lipase hydrolysis techniques, the proportions, compositions and structures of these novel triglyceride classes were determined. Four types of positional specificities in fatty acid combinations could be shown by our procedures. These are discussed and, on the basis of our results, some tentative proposals as to possible biosynthetic mechanisms are advanced.