[en] The nature of high velocity clouds HI is investigated. A model is proposed, capable of explaining the observed correlation Nsub(H) (-vsub(r)) in high negative velocity HI clouds. In this model the negative velocities are stipulated by cloud incidence upon the Galaxy plane. The mechanisms of high velocity cloud formation are discussed. A supernova explosion does not seem to account for this. Cloud generation behind the shock wave front produced in intergalactic gas interactions with the gaseous halo of the Galaxy appears to be a more tenable reason