Many natural radionuclides have been measured in regional groundwater, acid spring waters and brines in the vicinity of Lake Tyrrell, Victoria. The concentration of nuclides within the U and Th decay series range over several orders of magnitude. The acid groundwaters display very high Ac, Ra, 222Rn, 210Pb and 210Po activities in the springs on the western margin of the lake compared to those generally recorded in less saline and neutral groundwaters. This is an area of the lake margin where 226Ra and 228Ra have accumulated in shallow sediments. Measured and estimated distribution coefficients for 226Ra range from 10 to 800, which combined with flow rates places the source of the 226Ra within 5 km of the radioactive spring zone. 227Ac showed the strongest control by pH of all the measured radionuclides and was similar to Al in this behaviour. 210Pb and 210Po appear to be quite mobile at high salinity when pH was <5. U and Th concentrations were not generally very high in any combination of acid/saline waters except for elevated 228Th activities in the spring waters. These probably relate to high concentrations of its parent 228Ra in the waters.