Electron collisional as well as ion collisional effects have a significant effect on the stability analysis of lower hybrid drift modes in the ionosphere. Electron collisions stabilized the modes and cause a density gradient threshold for the instability not previously calculated. This threshold results in restrictions on the interpretation of 155- and 415-MHz backscatter results as being due to lower hybrid drift instabilities and suggests measurements to determine whether the instability can account for the backscatter.