From the radial velocity data for O-B5 stars within 3 kpc of the Sun the variation of the semi-axesΣ1 andΣ2 of the velocity ellipsoid in the solar region is estimated. It is found that both the semi-axes as well as their ratioΣ2/Σ1 decrease away from the galactic centre. The value ofΣ2/Σ1 changes from 1.17 atR=9 kpc to 0.48 atR=11 kpc passing through a value of 0.86 at the solar distance ofR0=10 kpc. These results are consistent with the usually assumed inverse square law of force in the outer regions of the galaxy.
