In connection with discrepancies between experimental and theoretical values for the vacuum polarization correction in the case of the 5-4 transitions in heavy and medium muonic atoms, the energies of this transition in /sup nat/Hg and /sup 203/Tl were measured at the CERN-SC muon channel. The broadening of the 2/sup +/-0/sup +/- nuclear gamma transition in muonic /sup 190/Os and /sup 192/Os was used to determine the magnetic h.f. splitting of the 2/sup +/ rotational state. The results are compared with the predictions of different models. (7 refs)