Thek _o-standardization method is based on analytical constants, which are -line related and the results are calculated from the peak areas of the -ray spectrum. Consequently, prerequisites of this method are the correct identification of the -lines and the avoidance of unresolved peak interferences. Because these problems are already solved with nuclide identification programs, a new variant of thek ^o-method was developed, using the activities of the nuclides instead of the peak areas. We introduced isotope related factors,k _i, calculated fromk _o-factors. The procedure is described and results are compared with those obtained by the -line based method.