  We present ROSAT PSPC and HRI observations of A2111, the richest galaxy
cluster photometrically surveyed by Butcher & Oemler (1984). The cluster
contains a distinct comet-shaped X-ray subcomponent, which appears hotter than
the rest of the cluster. The galaxy and X-ray surface brightness distributions
of the cluster show a similarly elongated morphology. These results suggest
that the cluster is undergoing a head-on subcluster merger. This merger may
also be responsible for the high fraction of gas-rich blue galaxies observed in
the cluster. We have further detected a poor cluster along the merging axis and
at a projected distance of about 5 Mpc from A2111.
