An experimental investigation was conducted to determine the structure and integrated properties of turbulent boundary layers at hypersonic speeds. These properties were deduced from pitot pressure and total temperature surveys made through the boundary layer at various locations on the wall of both a contoured and a conical nozzle. Tests were conducted at average Mach numbers of 11.89 and 10.83 respectively. The corresponding momentum Reynolds numbers ranged from 650 to approximately 1330. The data were obtained in the presence of both a favorable pressure gradient and heat transfer. The results indicate that the density distribution, the static temperature distribution, and the total enthalpy ratio versus the velocity ratio profiles through the boundary layer do not agree with the Crocco theory. The data also indicate that the sublayer is very thick and is approximately 25% as thick as the boundary layer itself. Depending upon the momentum Reynolds number, the sublayer can be either fully subsonic or partially subsonic and partially supersonic in nature. In addition, the transformed velocity profile data and the law of the wall in its incompressible form do not agree. Finally, the skin friction coefficient obtained from the Baronti-Libby transformation and Coles' law of corresponding stations is about 15% to 35% greater than that calculated using the Spalding-Chi semi-empirical technique. (Author).