Products of the gas-phase reactions of OH radicals with furan, furan-d(4), 2- and 3-methylfuran, and 2,3- and 2,5-dimethylfuran have been investigated in the presence of NO using direct air sampling atmospheric pressure ionization tandem mass spectrometry (API-MS and API-MS/MS), and gas chromatography with flame ionization and mass spectrometric detectors (GC-FID and GC-MS) to analyze samples collected onto annular denuders coated with XAD solid adsorbent and further coated with O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine for derivatization of carbonyl-containing compounds to their oximes. The 3 products observed were unsaturated 1,4-dicarbonyls, unsaturated carbonyl-acids and/or hydroxy-furanones, and from 2,5-dimethylfuran, an unsaturated carbonyl-ester. Quantification of the unsaturated 1,4-dicarbonyls was carried out by GC-FID using 2,5-hexanedione as an internal standard, and the measured molar formation yields were: HC(O)CH=CHCHO (dominantly the E-isomer) from OH + furan, 75 +/- 5%; CH3C(O)CH=CHCHO (dominantly the E-isomer) from OH + 2-methylfuran, 31 +/- 5%; HC(O)C(CH3)=CHCHO (a E-/Z-mixture) from OH + 3-methylfuran, 38 +/- 2%; and CH3C(O)C(CH3)=CHCHO from OH + 2,3-dimethylfuran, 8 +/- 2%. In addition, a formation yield of 3-hexene-2,5-dione from OH + 2,5-dimethylfuran of 27% was obtained from a single experiment, in good agreement with a previous value of 24 +/- 3% from GC-FID analyses of samples collected onto Tenax solid adsorbent without derivatization.