The formation of secondary organic aerosol (SOA) generated by irradiating 2-methyl-3-buten-2-ol (MBO) in the presence and/or absence of NO<sub>x</sub>, H<sub>2</sub>O<sub>2</sub>, and/or SO<sub>2</sub> was examined. Experiments were conducted in smog chambers operated either in dynamic or steady-state mode. A filter/denuder sampling system was used for simultaneously collecting gas and particle phase products. The structural characterization of gas and particulate products was investigated using BSTFA, BSTFA + PFBHA, and DNPH derivatization techniques followed by GC-MS and liquid chromatography analysis. This analysis showed the occurrence of more than 68 oxygenated organic compounds in the gas and particle phase, 28 of which were identified. The major components observed include 2,3-dihydroxyisopentanol (DHIP), 2-hydroxy-2-oxoisopentanol, 2,3-dihydroxy-3-methylbutanal, 2,3-dihydroxy-2-methylsuccinic acid, 2-hydroxy-2-methylpropanedioic acid, acetone, glyoxal, methylglyoxal, glycolaldehyde, and formaldehyde. Most of these oxygenated compounds were detected for the first time in this study. <br><br> While measurements of the gas phase photooxidation products have been made, the focus of this work has been an examination of the particle phase. SOA from some experiments was analyzed for the organic mass to organic carbon ratio (OM/OC), the effective enthalpy of vaporization (ΔH<sub>vap</sub><sup>eff</sup>), and the aerosol yield. Additionally, aerosol size, volume, and number concentrations were measured by a Scanning Mobility Particle Sizer coupled to a Condensation Particle Counter system. The OM/OC was found to be 2.1 in MBO/H<sub>2</sub>O<sub>2</sub> system. The ΔH<sub>vap</sub><sup>eff</sup> was 41 kJ mol<sup>−1</sup>, a value similar to that of isoprene SOA. The laboratory SOA yield measured in this study was found to be 0.7 % in MBO/H<sub>2</sub>O<sub>2</sub> for an aerosol mass of 33 μg m<sup>−3</sup>. Time profiles and proposed reaction schemes are provided for selected compounds. <br><br> The contribution of SOA products from MBO oxidation to ambient PM<sub>2.5</sub> was investigated by analyzing a series of ambient PM<sub>2.5</sub> samples collected in several places around the United States. In addition to the occurrence of several organic compounds in both field and laboratory samples, DHIP was found to originate only from the oxidation of MBO, and therefore this compound could serve as a tracer for MBO SOA. Initial attempts have been made to quantify the concentrations of DHIP and other compounds based on surrogate compound calibrations. The average concentrations of DHIP in ambient PM<sub>2.5</sub> samples from Duke Forest, NC ranged from zero during cold seasons in areas with low MBO emission rates to approximately 1 ng m<sup>−3</sup> during warm seasons in areas with high MBO emission rates. This appears to be the first time that DHIP has been detected in ambient PM<sub>2.5</sub> samples. The occurrence of several other compounds in both laboratory and field samples suggests that SOA originating from MBO can contribute under selected ambient conditions to the ambient aerosol mainly in areas where MBO emissions are high.