In M. Fiedler, T.L. Markham [Linear Algebra Appl. 173 (1992) 115] M. Fiedler and T.L. Markham studied a partition of Z-matrices. Here, a transformational characterization is given for Z-matrices in general as well as for each member of the Fiedler-Markham partition. This characterization generalizes the transformational characterization of nonsingular M-matrices given by C.R. Johnson and the author in (Linear Algebra Appl., to appear).