The Anatolian "Diagonal" divides Turkish Anatolia into two major zoo- and phytogeographical regions. Along this "Diagonal" a series of closely related species of vipers are distributed: Vipera bornmuelleri, Vipera bulgardaghica, and Vipera wagneri. To this series a new species, Vipera albazona sp. n. is added. The importance of this "Diagonal" as a mechanism for dispersal and speciation is also discussed.