Abstract: A continuously variable transmission mechanism incorporating co-axial spaced input and output rollers between which a variable ratio driving connection is established by discs which have flat faces engaged with the peripheries of the rollers. Axial movement of the assembly of discs varies their effective diameter and thus the drive ratio. A planetary gear set has one element rotatable with the input roller, a second element rotatable with the output roller and its third element constituted by a carrier and a planet gear connected to an output shaft. The engagement load between the rollers and discs is controlled in response to the torque being transmitted. The transmission provides a range of transmission ratios in a forward and reverse direction.