In this paper a theorem is presented which exhibits the dynamical structure of closed-loop discrete-time tracking systems by expressing the transfer-function matrices of such systems in terms of the controllable canonical form (Brunovsky 1966) of the matrix pair which characterizes the time-domain representation of such systems. This structure theorem is illustrated by determining the transfer-function matrix of a time-optimal discrete-time tracking system previously designed in the time-domain by Bradshaw and Porter (1975).