Gas-phase chemical mechanisms are a critical component of air quality models that are used to study atmospheric oxidants, secondary particulate matter and toxic air contaminants. Three-dimensional models require efficient, condensed chemical mechanisms and several are currently available including the Carbon Bond (CB) mechanism, Statewide Air pollution Research Center (SAPRC) mechanism and Regional Atmospheric Chemical Mechanism (RACM). The CB7, SAPRC-07 and RACM2 mechanisms are implemented in the Comprehensive Air quality Model with extensions (CAMx) Eulerian photochemical model enabling mechanism comparisons within a single model framework. For these mechanisms, we compared the tendency of volatile organic compounds (VOC) to produce ozone under so-called VOC-limited conditions where VOC reactivity is influential on ozone and oxidant production. Comparison to the SAPRC-07 mechanism was particularly useful for VOC-limited conditions because the mechanism was extensively tested against smog chamber data. We found that all three mechanisms produce similar trends in reactivity across VOC classes that include alkanes, alkenes, aromatics, alkynes, alcohols, aldehydes and ketones. Reactivity differences between mechanisms were more pronounced for the aromatics and terpenes that have complex chemical reaction pathways in the atmosphere. Differences also were noted for hydroxyl radical (OH) that could influence modelled atmospheric lifetimes of trace gases and the performance of model components that depend upon OH concentration (e.g., secondary aerosol schemes).