  We discuss the distribution and kinematics of neutral hydrogen in the halos
of spiral galaxies. We focus in particular on new results obtained for the
nearby Sc galaxy NGC 2403 which have revealed the presence of extended HI
emission (here referred to as the `beard') at anomalous velocities with respect
to the `cold' HI disk. Modeling shows that this component has a mass of about
1/10 of the total HI mass and is probably located in the halo region. Its
kinematics differs from that of the thin HI disk: it rotates more slowly and
shows radial inflow. The origin of this anomalous gas component is unknown. It
could be the result of a galactic fountain or of accretion of extragalactic
`primordial' gas.
