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 .