The single crystal and powder EPR spectra of Fe(VI) in the host structures K(2)MO(4) (M = Cr, S, Se) were analyzed with respect to the fine structure parameters D and E. In the case of K2SeO4, which possesses three structural modifications in dependence on temperature, the number of crystallographically inequivalent Fe(VI) positions and the changes of the extent of polyhedral distortion could be followed by passing the two phase transitions. AOM calculations were used in order to assign the various EPR signals to the different sites.