Chemical investigation of the Bulgarian species Tanacetum. parthenium, T. millefolium, T. achilleifolium, T. corymbosum and T. macrophyllum afforded in addition to 24 known sesquiterpene lactones a new 12, 8-eudesmanolide 22. Besides, four known highly oxigenated terpenoids and a new keto-diol 30 of the rare iphionane skeleton were also isolated. The structures were elucidated on the basis of their spectral properties. The accumulation of the different sesquiterpene lactones in the studied species and there classification is discussed.