Abstract: A top entry, trunnion-type ball valve has identical, but oppositely arranged sealing assemblies on both sides of the ball. These sealing assemblies include a seal carriage that holds and maintains in position an annular body seal, an annular ball seal and a resilient O-ring interposed therebetween. The O-ring is located in a cavity between the body seal and ball seal which is open to fluid in the valve through-passage and therefore subject to high pressure in the line. Pressure in the O-ring cavity forces the ball and body seals apart and causes the O-ring to compress and resiliently urge the ball and body seals into sealing engagement with the ball and body, respectively. Angled surfaces formed on the seals enhance sealing by concentrating contact pressures.