The ethyl acetate soluble extract of the dried roots of Ferula penninervis gave 17 new sesquiterpenes [15 of the guaiane-type, ferupennins A-O (1-15), and two of the eudesmane-type, 1alpha-hydroxy-2-oxo-5alpha,7beta,11betaH-eudesm-3-en-6alpha,12-olide (16) and penninervin (17)] and nine known sesquiterpenes. The structures of the new compounds were elucidated on the basis of spectroscopic evidence and X-ray analysis. The absolute configuration of ferupennin A (1) was determined by a modified Mosher method.