The liquid phase autoxidation of the readily available sesquiterpene valencene to the commercially important perfuming agent nootkatone utilizing gaseous oxygen at atmospheric pressure has been investigated. Catalyst systems involving transition metal salts and complexes, and phase-transfer catalysts have been evaluated under different conditions of valencene concentration, catalyst concentration, reaction temperature, solvent and oxygen flow rate. Of eighteen candidate catalysts for the oxidation of valencene to nootkatone, chlorocarbonylbis (triphenylphosphine) iridium (Vaska's catalyst) demonstrated good activity and appeared to show the best potential for future work.