The natural uranium decay series provide a suite of tracers to study transport processes in the ocean. We have used nuclides of the particle-reactive elements Th, Pa, Pb and Po for studies of particle flux in the Southern Ocean, whereas isotopes of the elements Ra and Ac served as tracers for the transport of water masses. Here we summarize the specific aspects of the behaviour of these nuclides in the Southern Ocean and give some examples of their application. We review the important influence of exchange between ocean basins by advection and upwelling on the long-lived nuclides. We show how the distribution of 234Th in surface waters across the ACC represents the export production, whereas in the benthic nepheloid layer this tracer is used to illustrate how the resuspension regime in the ACC is linked to the position of the oceanographic fronts.