  The recent discovery of two flux decrements in deep radio maps obtained by
the VLA and the Ryle Telescope can have powerful implications for the density
parameter of the Universe, $\Omo$. We outline these implications by modeling
the decrements as the thermal Sunyaev-Zel'dovich (SZ) effect from two clusters
assuming their properties are similar to those of the low redshift population.
In this case, the absence of any optical or X-ray counterparts argues that the
clusters must be at large redshifts. We highlight the difficulty this poses for
a critical cosmology by a comparison with a fiducial open model with $\Omo=0.2$
($\lamo=0$). Applying the phenomenological X-ray luminosity-temperature
relation needed to explain the EMSS cluster redshift distribution, as inferred
by Oukbir and Blanchard (1997), we convert the X-ray band upper limits to lower
limits on the clusters' redshifts. Comparison of the counts implied by these
two SZ detections with model predictions, for clusters with redshifts larger
than these lower limits, illustrates quantitatively the inability of the
critical cosmology to account for such high-redshift clusters. On the other
hand, the open model with $\Omo=0.2$ remains consistent with the existence of
the two objects; it possibly has, however, difficulties with current limits on
spectral distortions and temperature fluctuations of the cosmic microwave
background. The discussion demonstrates the value of SZ cluster searches for
testing cosmological models and theories of structure formation.
