A taxonomic study on the males of Palearctic species of Ephedrus Haliday is here reported. In addition to the morphological characters currently used in the species classification of the genus, male external genitalia are particularly taken into consideration. This character, even though not strictly species-specific, proves to be of noticeable interest in species discrimination, especially when combined with other morphological features. On this basis a new key for males of Palearctic species of Ephedrus is proposed.