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 0.3 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 .