  Open star clusters from the MWSC (Milky Way Star Clusters) catalogue have
been used to determine the Galactic rotation parameters. The circular rotation
velocity of the solar neighborhood around the Galactic center has been found
from data on more than 2000 clusters of various ages to be V_0=236+/-6 km
s^{-1} for the adopted Galactocentric distance of the Sun R_0=8.3+/-0.2 kpc.
The derived angular velocity parameters are \Omega_0=28.48+/-0.36 km s^{-1}
kpc^{-1}, \Omega'_0=-3.50+/-0.08 km s^{-1} kpc^{-2}, and \Omega"_0=
0.331+/-0.037 km s^{-1} kpc^{-3}. The influence of the spiral density wave has
been detected only in the sample of clusters younger than 50 Myr. For these
clusters the amplitudes of the tangential and radial velocity perturbations are
f_\theta=5.6+/-1.6 km s^{-1} and f_R=7.7+/-1.4 km s^{-1}, respectively; the
perturbation wavelengths are \lambda_\theta=2.6+/-0.5 kpc (i_\theta=-11+/-2
degrees) and \lambda_R=2.1+/-0.5 kpc (i_R=-9+/-2 degrees) for the adopted
four-armed model (m=4). The Sun's phase in the spiral density wave is
(\chi_\odot)_\theta=-62+/-9 degrees and (\chi_\odot)_R =-85+/-10 degrees from
the residual tangential and radial velocities, respectively.
