  We investigate the evolution of clusters of galaxies in a sample of distant
clusters with redshifts between 0.3 and 1.0. We show the abilities and
limitations of combined ROSAT and ASCA data to draw cosmological conclusions.
For the first time bolometric luminosities, masses, gas masses, gas mass
fractions, and iron masses are derived in such a distant sample in a consistent
way. We compare these quantities with the corresponding quantities in nearby
samples. Furthermore, we analyse relations between these quantities and the gas
temperature, metallicity and the morphological parameters and compare them with
relations in nearby samples. Fits to all relations with power law functions are
given. We find relations between X-ray luminosity, temperature, mass, gas mass,
core radius and beta, similar to those found in nearby clusters. Furthermore,
we find gas mass fractions increasing with radius, with the effect being
stronger in less massive clusters. Within errors we find no evidence for
evolution in any of the quantities nor in any of the relations. These results
favour a low Omega universe, but without strong constraints. We point out how
promising the next generation of X-ray satellites XMM, CHANDRA and ASTRO-E are
for cosmological studies with clusters. From the new observations primarily two
measurements are required: detection of more distant clusters and measurements
of the spectral and spatial parameters with much higher precision.
