15 new native and alien species of vascular plants are reported for the Irkutsk Region, Republic Buryatia, Trans-Baikal Territory: Agropyron michnoi Roshev., Arctopoa schischkinii (Tzvelev) Prob., Arnica intermedia Turcz., Atocion armeria (L.) Fourr., Cynodon dactylon Pers., Dracocephalum argunense Fisch. ex Link, Eragrostis minorHost, Festuca richardsonii Hook., Lespedeza davurica (Laxm.) Schi...