Environmental radioactivity research is more advanced for the (238)U series than for the (232)Th series, for a number of reasons. One reason is that some radionuclides of the (232)Th series are more difficult to measure than the corresponding isotopes in the (238)U series, and measurement techniques are less widely available. The (232)Th series population doses, however, are sometimes significant. This paper analyses some main radionuclides in the (232)Th series in comparison with corresponding nuclides in the (238)U series, with regard to measurement techniques, dose coefficients and regulation needs.