The kinetics of actinide and technetium redox reactions are important in many separations processes; for instance, in the reprocessing of irradiated nuclear fuel by the Purex process. In this process, the kinetics of reactions in both aqueous nitric acid and organic tributyl phosphate (TBP) solutions are important. Kinetic data are particularly necessary for the computer simulation of flowsheets and become increasingly important as the residence times in extraction contactors are reduced. Although a large body of literature exists, some potentially important process reactions have not been sufficiently studied for modeling purposes. Additionally, if new redox reagents are to be considered for process applications, their rates of reaction need to be determined. A program of work has been undertaken to: Compile known data for application in modeling of process flowsheets. Obtain kinetic data to fill in gaps in the literature. Study the kinetics of new redox reagents using conventional and stopped-flow techniques. This paper summarizes recent studies, including: U(IV) and Np(IV) oxidation by HNO3 in TBP phases. Tc(VII)-hydroxylamine reactions in the absence and in the presence of U(IV). Np(VI) and Pu(IV) reduction by a variety of new organic reductants, including oximes, substituted hydroxylamines, and hydroxamic acids. Kinetics of U and Np mass transfer in a single-stage centrifugal contactor.