We study in this paper the problem of disturbance decoupling with constant (i.e., static) measurement feedback (DDPCM) for linear systems. For a class of systems which have a left invertible transfer function from the control input to the controlled output or a right invertible transfer function from the disturbance input to the measurement output, we obtain a complete characterization of all solutions to the DDPCM. For a system that does not satisfy the above invertibility condition, we use the special co;ordinate basis to obtain a reduced-order system. Then a complete characterization of all possible solutions to the DDPCM for the given system can be explicitly obtained, if the obtained reduced-order system itself satisfies the invertibility condition. The main advantage of these solutions is that the solutions are given in a set of linear equations. This resolves the well known difficulty in solving non-linear equations associated with the DDPCM.