Spectrosopic techniques, such as UV-Visible spectrometry, can be deployed to observe the chemical changes taking place during fast reactions. However, in many cases the reaction timescales are too fast to be performed and observed by the simple manual mixing of the reactants in a cuvette. The stopped-flow technique is frequently used for rapid kinetics experiments allowing the reactants to mix effectively and react whilst monitoring the reaction in a low volume cuvette in the UV-Visible instrument. This application note demonstrates how the PerkinElmer LAMBDA 465 Diode Array UV-Visible Spectrophotometer together with the TgK Scientific SFA-20 Rapid Kinetics Accessory allows reaction monitoring on the millisecond timescale.