The determination of the relative and combined effects of surface roughness and mass transfer on turbulent boundary-layer development, and in particular, on skin-friction drag was the prime objective of this study. Wind-tunnel tests were conducted in the NSWC Boundary-Layer Channel at a freestream Mach number of 2.9. The thick nozzle-wall boundary layer in the facility was subjected to a systematic variation of surface roughness and mass transfer conditions. Boundary-layer pressure and temperature surveys were obtained and skin friction was measured directly using a skin-friction balance which had a provision for active blowing through the floating drag element. Data comparisons with skin-friction theories and law-of-the-wall velocity profile correlations are presented. (Author).