  We present the X-ray luminosity function (XLF) of the ROSAT Brightest Cluster
Sample (BCS), an X-ray selected, flux limited sample of 172 clusters of
galaxies at $z\leq 0.3$ compiled from ROSAT All-Sky Survey data. While the bulk
of the BCS consists of Abell clusters, the sample also contains Zwicky clusters
and purely X-ray selected systems. The BCS-XLF represents the best
determination of the local X-ray luminosity function for galaxy clusters and
thus provides an important reference for evolutionary studies. For the BCS
itself, we find no convincing evidence for cluster evolution within a redshift
of $z=0.3$. This result is not in conflict with the findings of the EMSS study
on cluster evolution.
