  VLBI measurements of the absolute proper motions of 23 radio stars have been
collected from published data. These are stars with maser emission, or very
young stars, or asymptotic-giant-branch stars. By comparing these measurements
with the stellar proper motions from the optical catalogs of the Hipparcos
Celestial Reference Frame (HCRF), we have found the components of the residual
rotation vector of this frame relative to the inertial coordinate system:
(\omega_x,\omega_y,\omega_z) = (-0.39,-0.51,-1.25)+/-(0.58,0.57,0.56) mas/yr.
Based on all the available data, we have determined new values of the
components of the residual rotation vector for the optical realization of the
HCRF relative to the inertial coordinate system: (\omega_x,\omega_y,\omega_z) =
(-0.15,+0.24,-0.53)+/-(0.11,0.10,0.13) mas/yr.
