We present and discuss the X-ray luminosity function ( XLF ) of the ROSAT Brightest Cluster sample ( BCS ) , an X-ray flux limited sample of clusters of galaxies in the northern hemisphere compiled from ROSAT All-Sky Survey data .
The BCS allows the local cluster XLF to be determined with unprecedented accuracy over almost three decades in X-ray luminosity and provides an important reference for searches for cluster evolution at higher redshifts .

We find the significance of evolution in both the XLF amplitude and in the characteristic cluster luminosity L _ { X } ^ { \star } to be less than 1.8 \sigma within the redshift range covered by our sample thereby disproving previous claims of strong evolution within z \la 0.2 .