An investigation was conducted in a hypersonic shock tunnel to study the laminar boundary layer transition on a highly cooled 10-degree cone of 4-foot length over the Mach number range of 8.5 to 10.5 with a stagnation temperature of 1400K. The effects on transition of tip surface roughness, tip bluntness, and =2-degree angle of attack were investigated. With fast response thin film surface heat transfer gauges, it was possible to detect the passage of turbulent bursts that appeared at the beginning of transition. It was found that the surface roughness greatly promoted transition in the proper Reynolds number range. The Reynolds number for the beginning and end of transition at the 8.5 Mach number location were 3,800,000 to 9,600,000 and 2,200,000 to 4,200,000 for the smooth sharp tip and rough sharp tip, respectively. The local skin friction data agreed with the heat transfer data through Reynolds analogy. The tip bluntness data showed a strong delay in the beginning of transition for a cone base to tip diameter ratio of 20, approximately a 35% increase in Reynolds number over that of the smooth sharp tip case. The angle of attack data indicated the cross flow to have a strong influence on transition by promoting it on the sheltered side of the cone and delaying it on the windward side. (Author).