Abstract: Some natural Lathyrus aphaca L. varieties have been investigated from chemotaxonomic point of view. Seed fatty acid composition of four L. aphaca varieties (affinis, biflorus, pseudoaphaca and modestus) of genus Lathyrus was determined and their taxonomic relationships were also evaluated using chemical and numerical taxonomic techniques. The Lathyrus aphaca varieties seed contained profitable composition of poly-unsaturated fatty acids, linoleic and palmitic acid. The lowest fatty acid component was margaric, pentadecanoic and myristic acid. It is determined that the seed lipids contained a relatively large proportion of un-saturated fatty acids with linoleic acid as predominant. The results showed that intraspecific variation of fatty acid patterns was low in L. aphaca varieties with the exception of modestus, which was found partly different by fatty acid composition from the others.