Based on the statistical parallaxes, the mean absolute magnitudes and the spatial kinematical parameters were determined as functions of the periods for Mira variables given in the GCVS-4 and selected stars for which new kinematical data were obtained during the last decade. The BC were derived for the oxygen-rich Miras and the P–L relation was compared with predictions from pulsation theory. The following findings result from this analysis:
1) With respect to Miras, the GCVS-4 is complete down to V = 9m.
2) The kinematical and orbital parameters indicate a higher age for the oxygen-rich Miras pulsating with smaller periods.
3) The M
bol-period relation of the oxygen-rich Miras shows a low dispersion and does not depend on the pulsation mode. The resulting P–L relation is a superposition of P–L relations of different pulsation modes.
4) The fraction of the fundamental mode pulsators decreases with increasing pulsation period.