Abstract: A rotary-radial internal combustion engine wherein a piston-containing cylinder housing and cam means are mounted in an engine housing for relative rotary motion with respect to each other; said cylinder housing including diametrically opposite combustion chambers having mounted for reciprocation therein rigidly linked pistons provided with cam follower means engaging said cam means; said engine housing being provided with fuel intake means for feeding pressurized fuel to said combustion chambers, means for firing said fuel in said combustion chambers, and burnt fuel scavenging means for exhausting burnt fuel from said combustion chambers; the combination of said relative rotary motion between said cylinder housing and said cam means, and said reciprocatory motion of said pistons, producing per engine revolution piston thrusts numerically greater than the number of combustion chambers in said cylinder housing; said piston thrusts being translated into torque which is applied to an engine drive shaft.