  We have studied dF-dK and dM stars belonging to Praesepe in order to
determine membership via radial velocities and to compare several stellar
properties, such as X-ray luminosities, H$\alpha$ equivalent width, etc,
between this cluster and Hyades, which have similar age. We show that all
properties are analogous in both clusters except the distribution of Lx. This
fact could be related to difficulties in the analysis of the Lx upper limits or
to more fundamental reasons, such as binarity rates and differences in the
properties of the binaries of each cluster.
