Vertical bubble velocities in equatorial spread F have been investigated analytically by Ott [1978>, Ossakow and Chaturvedi [1978>, and Hudson [1978>, all of whom found a proportionality of the vertical velocity to bubble depletion density. If the depletion density increases with height for a convectively growing bubble formed at the bottom of the F layer, then the vertical bubble velocity should increase with height also. In this paper we present VHF radar observations of equatorial spread F that support the latter conclusion.