The weak scattering, thin screen theory of scintillation of radio stars and satellites has been applied, in a mathematically rigorous way, to the observations of the plasma density structure deduced from rocket and radar measurements during equatorial spread F conditions. It is shown that bottomside spread F is capable of producing moderate scintillation at VHF, but not at gigahertz frequencies. Upwelling regions of depleted plasma density however, such as those described in several recent publications, are shown to have properties that could cause intense VHF scintillation as well as scintillations in the gigahertz range.