Softwood lignin was pyrolyzed to afford a “bio-oil” distillate in which phenols were major products. Extraction with alkali gave a range of lignin-related phenols having molecular weights (MWs) from 110 to 344 amu. The total phenolic extract was at least equal in antioxidant activity to the synthetic compound 2,6-di(tert)butyl-4- methylphenol (BHT). The extract was separated by chromatographic techniques to characterize components potentially responsible for the activity. A series of phenols in the extract exhibited MWs of 274, 302, 316, 330, and 344 and are likely to be dimers responsible for the majority of the observed antioxidant properties. Several of these compounds appear by mass spectrometry to be bifunctional phenolic compounds containing catechol or guaiacol groups. We hypothesize that a type of effective antioxidant for fatty acid esters will contain one phenolic hydroxyl group hydrogen-bonded to the ester and another at a radical-quenching site; monophenols are likely to be ineffective in this system due to the predominance of hydrogen bonding (kinetic solvent effect).