  We present preliminary observational results on tidal synchronization in
detached solar-type binary stars in the open clusters M35 (NGC2168; ~ 150 Myr)
and M34 (NGC1039; ~ 250 Myr). M35 and M34 provide populations of close
late-type binaries with ages that make them attractive observational tests of
models of tidal synchronization during the early main-sequence phase. A
combined dataset of stellar rotation periods from time-series photometry and
binary orbital periods and eccentricities from time-series spectroscopy enables
us to determine the angular rotation velocity of the primary star and the
orbital angular velocity at periastron. Comparison of the stellar and orbital
angular velocities provides information about the level of synchronization in
individual binary stars.
