Two secondary organic aerosol (SOA) formation modules have been implemented into a global chemical transport model (Model for Ozone And Related chemical Tracers, Version 2) to estimate the global distribution of SOA and to compare between methods. The first SOA model is based on bulk smog chamber yields while the second uses the gas to particle partitioning theory to predict SOA concentrations. Maximum SOA concentrations using the bulk yield method were found to vary up to 10 ¿g/m3 with concentrations peaking over the southeast United States, Europe, South America, central Africa, and southern Asia. Maximum SOA concentrations were found over the Northern Hemisphere (NH) and tropics in June while SOA concentrations in the tropics remained high through December. SOA production was found to be dependant on oxidant availability rather than volatile organic compound emissions in South America and Asia. Using the partitioning model, SOA concentrations peaked at 10 ¿g/m3 over South America in September related to organic carbon aerosol availability. The partitioning model produced significantly less SOA during the NH summer, and SOA production was found to be dependant on organic carbon primary aerosol and oxidant availability for South America and Asia. The total annual global production of SOA was calculated to be 24.6 Tg/yr using the bulk yield method and 15.3 Tg/yr using the partitioning method.