Two new sesquiterpene lactones of the eudesmanolide type, [6α-hydroxy-5,7αH,8βH-eudesm-4(15)-en-8,12-olide and 4β,6α-dihydroxy-5,7αH,8βH-eudesman-8,12-olide] were isolated from the aerial parts of Tanacetum ferulaceum, together with various other already-known substances: the sesquiterpene lactones, costunolide, tatridin A, 11,13-dihydrotatridin A, tatridin B, spiciformin, lα,10β-epoxydeacetyllaurenobiolide and deacetyl-β-cyclopyrethrosin, the flavonoids, apigenin, axillarin and 4′,5,7-trihydroxy-3,6-dimethoxyflavone, the coumarins, scopoletin and scoparone, and sitosterol and sitosteryl β-d-glucoside. © 1990.