  The present state of X-ray observations of cool stars in coeval open clusters
is reviewed. Concentrating on ROSAT results for solar-type stars, the available
observational dataset is summarized along with those details of the evolution
of X-ray activity of low mass stars which have been firmly established as a
result. Observational questions which are as yet unresolved are then addressed,
including the origin of ``supersaturation'' and whether observations of one
cluster can represent the X-ray properties of all clusters at the same age. The
role of high spatial resolution X-ray imaging as a tool for identifying cluster
members is highlighted and the prospects for future developments with AXAF and
XMM are discussed.
