Continuously variable speed power transmission with and without integrated motor/generator components. The transmission has an input member rotatable about an input axis, an output member rotatable about an output axis, a reaction control rotor with optional integrated motor/generator components for selective rotation about the input axis, a pericyclic motion converter mounted for pericyclic motion about the input axis, and a control means for selectively adjusting the rate of rotation of the reaction control rotor relative to the input member. A bevel gear construction is a preferred embodiment of the transmission. A method for varying speed ratios using pericyclic motion is described.