Abstract : A separated flow field, in which its incoming boundary layer is undistrubed up to the separation point, is defined as a base type flow. Examples of such flows are: the flows over a blunt base and over a backward facing step. The Corcco-Lees theory is applied to the supersonic, two-dimensional laminar base type flows defined above. The separated flow is divided into a mixing region and a recompression (or reattachement) region. Calculations of base pressure show its dependence on the Mach number and on two Reynolds number dependent variables. It is shown that existing base pressure data can be explained by these results. (Author)