Toluene, one of the principle aromatic compounds present in the atmosphere, is oxidized by OH to produce cresol and other products. Here later-generation low-volatility oxygenated products from cresol oxidation by OH are detected in the gas and particle phases. This work identifies a simple and significant mechanism for toluene secondary organic aerosol formation through the cresol pathway. Likely the phenolic pathway of other aromatic compounds is also important for secondary organic aerosol.