An analytical treatment of plane kinematics can be based upon the concepts of instantaneous invariants and canonical systems of reference . Instantaneous invariants have been introduced by O. Bottema ; they are geometrical invariants under the group of similitudes. The aim of this paper is to extend the said concepts to spatial kinematics. To this end we present an analytical treatment of spatial motion, which is as far as possible analogous to that of plane motion as given in . We insert applications of the theory to obtain results, which are partly classical and partly believed to be new.