The OH radical is one of the most important species in tropospheric chemistry and global climate change. In addition to controlling the lifetimes of many important atmospheric species, OH initiates the oxidation of carbon monoxide and hydrocarbons, which in the presence of nitrogen oxides can lead to the production of ozone in urban, rural and remote environments. The overall goal of this career development plan is to contribute new insights into the rapid and complex chemistry of the troposphere through laboratory experiments and ambient air measurements of OH and HO2, and integrate this research area into the classroom through a hands-on, project-based laboratory curriculum for undergraduate and graduate courses in atmospheric chemistry and environmental science. The plan involves the construction of a new laser-induced fluorescence instrument capable of making reliable measurements of OH and HO2 with high sensitivity. The instrument will be utilized in the laboratory to study the chemical kinetics of non-methane hydrocarbon oxidation, in smog chamber experiments to measure OH and HO2 under a variety of controlled conditions, and in ambient air as part of research field campaigns. The educational component of this CAREER project will allow students to obtain and analyze measurements of OH and HO2 in conjunction with measurements of O3, CO, and NOx.