  Measurements of the Cosmic Microwave Background Radiation (CMBR) provide a
powerful tool for measuring the primary cosmological parameters. However, there
is a large degree of parameter degeneracy in simultaneous measurements of the
matter density, Omega_m, and the Hubble parameter, H_0. In the present paper we
use the presently available CMBR data together with measurements of the
cosmological baryon-to-photon ratio, eta, from Big Bang nucleosynthesis, and
the relative mass fraction of baryons in clusters to break the parameter
degeneracy in measuring Omega_m and H_0. We find that present data is
inconsistent with the standard Omega=1, matter dominated model. Our analysis
favours a medium density universe with a rather low
  Hubble parameter. This is compatible with new measurements of type Ia
supernovae, and the joint estimate of the two parameters is Omega_m =
0.45^{+0.07}_{-0.07} and H_0 = 39^{+14}_{-13} km s^-1 Mpc^-1. We stress that
the upper bound on the Hubble parameter is likely to be much more uncertain
than indicated here, because of the limited number of free parameters in our
analysis.
