The accuracy of Reynolds-averaged Navier-Stokes calculations of axisymmetric high-speed afterbody flows is investigated. An approximate truncation error analysis is used to identify specific regions where discretization errors are large, and grid refinement is used to evaluate global solution accuracy. Good alignment of grid lines with streamlines in the shear layer at the nozzle exit is found to be important for obtaining solutions at high nozzle pressure ratios. Solution-adapted grids are used, and solutions that are essentially grid-independent are obtained. Modifications to the k-model for Mach number and streamline curvature effects are presented and validated in flows unrelated to base flows. In base flow calculations, these model modifications produce changes hi base drag in excess of 20%. Computed solutions agree well with experiment for base pressure and flow structure. Nomenclature a = sound speed C = turbulence modeling coefficient h = distance between grid nodes k = turbulence kinetic energy per unit mass L = symbolic representation of governing equation M = Mach number, U/d NPR = nozzle pressure ratio, PJ/POO p = pressure P k -rate of production of pk in Eqs. (6) and (7) q = flow variables Re = Reynolds number U,V = mean velocities x,r = spatial coordinates, normalized by body radius d = shear layer thickness 3^ = Kronecker delta e = rate of dissipation of k per unit mass /A = viscosity p = density a = model coefficients Tfj = stress tensor Subscripts h = associated with grid spacing h j = nozzle exit conditions t = turbulent oo = freestream conditions Model Designations STD = standard k-e model, Eqs. (5-7) M = with Mach number modification, Eq. (8) C = with curvature modification, Eqs. (9-11) MC = with both M and C modifications