The absolute and convective instability characteristics of supersonic wake dominated shear layers, described by a hyperbolic-tangent profile plus a wake component represented by a Gaussian distribution, are investigated. The effects of the Mach number, the freestream temperature ratio and the wake deficit on the boundary of the absolute/convective transition and the branch point parameters (such as frequency, wave number, and the spatial growth rate) are studied using linear stability theory. For supersonic mixing layers, it is found that at a given wake deficit the amount of backflow necessary to cause absolute instability decreases as the convective Mach number increases and that all the branch point parameters vary slowly as functions of the convective Mach number as opposed to subsonic mixing layers. As the wake deficit decreases, the curve separating the absolute and the convective regions moves down to the values of more negative freestream velocity ratio for both subsonic and supersonic mixing layers and the branch point spatial growth rate decreases for a given convective Mach number. The effect of decreasing the wake deficit on the absolute/convective transition boundary is similar to that of increasing the freestream temperature ratio. ©1997 American Institute of Physics.