Abstract: The present invention relates to a convertible skate comprising a shoe assembly including a flanged beam attached to and extending downwardly from a sole plate which is attached to the bottom of the shoe and a skate assembly including a channel having inwardly extending flanges extending laterally from the sides of the channel and adapted to extend between the sole plate and the outwardly laterally extending flanges of the beam. The flanged channel may bear roller skating trucks or it may bear pedestals attached to a blade adapted for ice skating. This invention also relates to three-wheeled roller skates having a single central front roller ball wheel and a rear truck having a pair of conventional, disc-shaped wheels. The surface of the roller ball has a plurality of continuous, circular grooves perpendicular to an axis of rotation of the roller ball which lies in a plane parallel to the surface engaged by the surface of the roller ball.