Thirteen seed characters have been studied in thirty eight species distributed over five genera representing tribe Trifolieae (family Leguminosae). The results obtained supported the separation of both genera Ononis and Trifolium, each in a separate subtribe as proposed by previous works. The genera Trigonella and Melilotus have variable characters which can be used in the subscription of their species. Species of Medicago have characteristic seed of their own which enables the separation of the genus in a separate subtribe Medicagonieae. Keys to the studied species within the genera Ononis, Trigonella, Melilotus and Trifolium have been constructed.