Abstract: A reaction kinetics measuring system which provides for the application of great variety of reaction initiating methods, as temperature or pressure or electrical field jump methods, mixing methods, flash photolysis method, and combinations of said methods, and for various optical detection methods, as absorption or fluorescence or scattered light or polarized light detection methods. The system features quickly and easily interchangeable optical elements in a number of optical paths, and a multitude of selectively usable measuring cells to adapt the system to the reaction initiating and detection methods used so that reliable and exactly reproducible results are obtained, which are comparable even if obtained under widely differing conditions.