ESDU Aero W.S.02.03.07 gives methods for turbulent or laminar boundary layers at the trailing edge. In the former case curves are given for two empirically determined contributions to the base pressure@ one of which is a function only of freestream Mach number and the other a function only of the ratio of the base thickness to the boundary layer momentum thickness at the base. The method predicts base pressure coefficient to within 0.02 and so use of flat plate data to determine the momentum thickness is adequate. The effect of incidence up to 5 degrees for freestream Mach numbers up to 4 is negligible. For the laminar case it is found that the base pressure depends on the position of transition in the wake; base pressure is a minimum when transition is in the separated layers and a maximum when transition occurs downstream of the confluence of the separated layers. A graph plots the extreme values of base pressure coefficient as a function of freestream Mach number but@ as transition position cannot be predicted readily@ the value between those extremes appropriate to given conditions is indeterminate.