  We emphasize the use of high-resolution CO line observations to derive
central rotation curves of galaxies. We present an example for high-resolution
interferometer observations of NGC 3079, and discuss the PV diagram and derived
rotation curve. The CO central rotation curves are combined with the outer
curves from \ha and HI-line observations to obtain total RC. We show that well
resolved RCs for massive galaxies generally start from non-zero velocities at
the nucleus.
