The mechanisms of a variety of chemical, physical, and biological processes are now understood more clearly as a result of picosecond spectroscopic studies. The identification of metastable species and transient states and the measurement of their formation and decay kinetics are made possible by means of picosecond emission and absorption spectroscopy. The data from these studies provide detailed mechanistic information about a reaction as it evolves. In this paper, we describe a laser system used for picosecond spectroscopy along with several chemical applications of picosecond absorption and emission spectroscopy performed in our laboratories. These include studies on the photochemical generation of trimethylenemethane biradicals from azo compounds, excited-state relaxation dynamics of p-dimethylaminobenzonitrile, and photodissociation of haloaromatic compounds.