Evolution of X-ray Luminous Clusters from z=0.3 to z=0.8

Observations of the highest redshift clusters provide the longest lever arm in the attempt to evaluate the evolution of their bulk properties. I present the most recent results on galaxy cluster evolution based on data from the ROSAT North Ecliptic Pole survey. At $z>0.3$ there is a deficit of clusters with respect to the local universe which is significant at $>$ 4.7$\sigma$. The evolution appears to begin at L$_{0.5-2.0} > 1.8\times10^{44}$ erg s$^{-1}$ in the NEP survey data and goes in the same direction as the original EMSS result. At lower redshifts there is no evidence for evolution, a result in agreement with all the existing cluster surveys.