WIDESPREAD HIGH-VELOCITY GAS IN THE SPIRAL GALAXY NGC-6946

21-cm line observations of the nearly face-on Sc galaxy NGC 6946 show HI at high velocities of up to +/- 100 km sec-1 with respect to the di fferentially rotating disk. Although the mass of the high-velocity com ponent is only about 5 10(8) M. - just a few percent of the total HI m ass of NGC 6946 - its total kinetic energy is about 10(55) erg, compar able to the total kinetic energy in the random motions of the HI disk. This ''high velocity'' HI is predominantly seen in the direction of t he bright optical disk and near the holes in the HI distribution. It i s likely to be located in the halo and swept up from the disk by stell ar winds and supernovae. It may be similar to the neutral gas found in the halo of our Galaxy and to the filaments and loops of ionized gas recently seen up to a few kpc from the plane in edge-on galaxies.