Abstract: A castor assembly is disclosed which includes a bearing block having a first bore for mounting a pintle, a second bore for mounting the spindle of a self-laying track member, and a downwardly open socket for mounting the trunnions of a castor roller. The pintle supports the bearing block on a frame or other structure for rotation about a vertical axis. The castor roller turns in its socket about a horizontal axis which is laterally spaced from the vertical axis. The track member is formed with an inner circular track which is in rotatable contact against the castor roller, and an outer circular edge of the track member encloses the roller and turns in close-spaced relationship with a lower truncated edge of the bearing block. The spindle of the track member rotates about an inclined axis lying in a plane passing through the horizontal axis. The inclined axis extends downwardly at an optimum angle which achieves a smooth castoring action when in operation.