The novel sesquiterpenoid 8alpha-hydroxyhypoglabric acid (1) was isolated from a methanolic extract of whole plants of Hypochaeris achyrophorus L. The compound was isolated by silica gel column chromatography (CC), repeated Sephadex LH-20 CC, and semi-preparative RP-HPLC. Structure elucidation was accomplished by high resolution mass spectrometry and by 1D- and 2D-NMR spectroscopy. The chemosystematic significance of the new compound is discussed in the context of sesquiterpenoids from other members of the Hypochaeridinae and in the light of recent molecular data on the phylogeny of this group.