  We have re-estimated the surface density of the Galactic disk in the solar
neighborhood within $\pm$ 0.4 kpc of the Sun using parallaxes and proper
motions of a kinematically and spatially unbiased sample of 1476 old bright red
giant stars from the Hipparcos catalog with measured radial velocities from
Barbier-Brossat & Figon (2000). We determine the vertical distribution of the
red giants as well as the vertical velocity dispersion of the sample, (14.4
$\pm$ 0.26 km/sec), and combine these to derive the surface density of
gravitating matter in the Galactic disk as a function of the galactic
coordinate $z$. The surface density of the disk increases from 10.5 $\pm$ 0.5
$M_{\odot}$ / pc$^2$ within $\pm$ 50 pc to 42 $\pm$ 6 $M_{\odot}$ / pc$^2$
within $\pm$ 350 pc. The estimated volume density of the galactic disk within
$\pm$ 50 pc is about 0.1 $M_{\odot}$ / pc$^3$ which is close to the volume
density estimates of the observed baryonic matter in the solar neighborhood.
