A study of the relationship between outside air ventilation rate and concentrations of volatile organic compounds (VOCs) generated indoors was conducted in a call center office building. The building, with two floors and a floor area of 4,600 m2, was located in the San Francisco Bay Area, CA. Ventilation rates were manipulated with the building's four air handling units (AHUs). VOC concentrations in the AHU returns were measured on seven days during a 13-week period. VOC emission factors were determined for individual zones on days when they were operating at near steady-state conditions. The emission factor data were subjected to principal component (PC) analysis to identify groups of co-varying compounds. Potential sources of the PC vectors were ascribed based on information from the literature supporting the associations. Two vectors with high loadings of compounds including formaldehyde, 2,2,4-trimethyl-1,3- pentanediol monoisobutyrate, decamethylcyclopentasiloxane (d5 siloxane), and isoprene likely identified occupant-related sources. One vector likely represented emissions from building materials. Another vector represented emissions of solvents from cleaning products. The relationships between indoor minus outdoor VOC concentrations and ventilation rate were qualitatively examined for eight VOCs. Of these, acetaldehyde and hexanal, which were likely associated with material sources, and d5 siloxane exhibited general trends of higher concentrations at lower ventilation rates. For other compounds, the operation of the building and variations in pollutant generation and removal rates apparently combined to obscure the inverse relationship between VOC concentrations and ventilation. This result emphasizes the importance of utilizing source control measures, in addition to adequate ventilation, to limit concentrations of VOCs of concern in office buildings.