Data are presented for the4He and222Rn contents and14C ages of groundwater from two artesian aquifers in southern Africa. The relative importance of helium derived from the decay of uranium and thorium in the aquifers is assessed, as well as “weathering” release of stored helium, fluxes into the aquifer, and diffusive losses. It is demonstrated that a4He flux originating from rocks below the aquifer is the most important source. The magnitude of this flux is relatively constant over the sampled intervals and is qualitatively estimated to be in the range 1 x 10−3to 3 x 10−2m1nHe m−2year−1(9 x 104to 3 x 106atoms He cm−2s−1). The4He data cannot be used to calculate the absolute age of the groundwater, but may be used to estimate the relative age and flow direction of very old groundwater if the4He flux rate is assumed, or known to be reasonably constant. Examination of the222Rn data suggests that they may have a useful application in the qualitative determination of the uranium content and porosity of aquifers.