The leaf epidermis of 14 Onosma L. species was examined by light and scanning electron microscopy (SEM). The leaf characters studied showed some variations. Morphologic features of the epidermal cells such as shape, structure of the anticlinal walls, stomatal size, outer stomatal rims, peristomatal rims, and apertures were summarised in the examined taxa. It was found that these characters are variable in the genus but usually they are stable within a species. Epidermal cells of the investigated taxa are polygonal, elongated, or irregular. Anticlinal walls of the epidermal cells are generally straight to curved and repand. Apertures are long, ellipsoidal, and narrow. SEM studies in particular provided some useful information concerning the systematics of Onosma taxa.