Forty-eight species of Astragalus L. sections Onobrychoidei DC., Uliginosi Gray and Ornithopodium Bunge (Fabaceae) in Turkey were studied in order to describe and investigate their seed morphologies and to evaluate the diagnostic value of this character using a stereoscopic microscope and a scanning electron microscope (SEM). SEM pictures of seeds were taken as a whole and in detail. The systematic implications of the findings are discussed. Six main seed types were observed. A key to identifying the different seed types is provided.