Pulicaria species, such as Pulicaria undulata, are rich in sesquiterpene lactones. The methylene chloride/ methanol (1:1) extract of P. undulata resulted in the isolation of new sesquiterpenes (1–4), as well as previously reported metabolites (5–14). Structures were elucidated by spectroscopic analyses. Using a mouse peritoneal macrophage bioassay, lipopolysaccharide-induced nitric oxide inhibition was observed with the eudesman-type sesquiterpene 1b,4b-dihydroxy-5aH,7aH,8a-guaia-10(14),11(13) dien-8b,12-olide (11) at an EC50 of 7.2 mM.