Biogenic volatile organic compound emissions from terrestrial ecosystems are now widely recognized to play significant roles in both regional air quality by affecting ozone formation and in controlling the oxidizing capacity of the global atmosphere and hence the lifetimes of reactive gases such as methane and nitrous oxide. Recent observations (Goldstein et al., 2004; Di Carlo et al., 2004; Claeys et al., 2004) suggest that terrestrial ecosystems may also emit a range of very reactive biogenic volatile organic compounds (VR-BVOCs) that affect atmospheric chemistry and secondary aerosol formation. Direct measurements of emissions rates of these compounds are difficult because of their high reactivities (potentially lifetimes less than 1 minute in the presence of ozone) and low vapor pressures. Sesquiterpenes (C₁₅H₂₄) are an important component of these VR-BVOCs. Although the ability of plants to emit sesquiterpenes has been understood previously, new measurement techniques are dramatically increasing estimates of production. We have developed a novel cuvette and analytical system for measuring sesquiterpene emissions from plants in arid ecosystems. This system minimizes plant disturbance and provides for controlled conditions to assess in situ production rates of sesquiterpenes. We hypothesize that the high air temperatures of the Mojave Desert will drive significant emissions of sesquiterpenes dominant species (e.g., creosote bush, Larrea tridentata) and that these emissions will affect regional air quality in rapidly expanding urban areas such as Las Vegas.