The constancy of the slope of the initial mass function in the Galactic disk

Results of an investigation of the initial mass function (IMF) in the spiral arms of Perseus, Orion and Sagittarius as well as of the solar neighbourhood are presented. The IMF slope is shown not to depend on the galactocentric radius at distances up to 5 kpc from the Sun. The IMF is approximated by the function: f(lg M) ≡ M^-1.4±0.22 in the mass interval from 0.3 to 25 M_sun; and f(lg M) ≡ M^-1.83±0.30 from 16 to 125 M_sun;. It is noted that the increase of the IMF slope for massive stars seems to be due to underestimation of observational selection, stellar wind etc., but not a real effect.