  We have conducted a kinematic study of 165 young M dwarfs with ages of <300
Myr. Our sample is composed of stars and brown dwarfs with spectral types
ranging from K7 to L0, detected by ROSAT and with photometric distances of <25
pc assuming the stars are single and on the main-sequence. In order to find
stars kinematically linked to known young moving groups (YMGs), we measured
radial velocities for the complete sample with Keck and CFHT optical
spectroscopy and trigonometric parallaxes for 75 of the M dwarfs with the
CAPSCam instrument on the du Pont 2.5-m Telescope. Due to their youthful
overluminosity and unresolved binarity, the original photometric distances for
our sample underestimated the distances by 70% on average, excluding two
extremely young (<3 Myr) objects found to have distances beyond a few hundred
parsecs. We searched for kinematic matches to 14 reported YMGs and identified 9
new members of the AB Dor YMG and 2 of the Ursa Majoris group. Additional
possible candidates include 6 Castor, 4 Ursa Majoris, 2 AB Dor members, and 1
member each of the Her-Lyr and beta Pic groups. Our sample also contains 27
young low-mass stars and 4 brown dwarfs with ages <150 Myr which are not
associated with any known YMG. We identified an additional 15 stars which are
kinematic matches to one of the YMGs, but the ages from spectroscopic
diagnostics and/or the positions on the sky do not match. These warn against
grouping stars together based only on kinematics and that a confluence of
evidence is required to claim that a group of stars originated from the same
star-forming event.
