Abstract: A multistage speed reducer for high speed rotation including a planetary roller friction reducer for the first stage reducer and a geared reducer for the second stage reducer, the planetary roller friction reducer having its output shaft also used as the input shaft of the geared reducer. Such an arrangement permits transmission of a very high speed and large horsepower rotation at a relatively high reduction ratio with low noise while at the same time consuming less space. The speed reducer may preferably be equipped with safety means for excessive torques.