  We performed a systematic and comprehensive estimate of the Hubble constant
$H_0$ via the Sunyaev-Zel'dovich temperature decrement and the X-ray
measurements for clusters up to the redshift $z=0.541$, with particular
attention to its dependence on the density parameter $\Omega_0$, and the
cosmological constant $\lambda_0$. The resulting values of $H_0$ are largely
consistent with that derived from the Cepheid distance for nearby galaxies. We
discuss how the angular diameter distance $d_A$ vs. $z$ diagram from the
accurate SZ measurements of high-$z$ clusters can distinguish the values of
$\Omega_0$ and $\lambda_0$.
