Editorial Policy

Consider the parametric linear complementarity problem w=Mz+q+p, w0, z0, w^Tz=0, where p0, 0q0, and 0. We show that a necessary condition for every complementary map z() to be isotone for every nonzero q0 and every p is that M be either a P-matrix or a -matrix. The Cottle necessary and sufficient conditions for strong and uniform isotonicity for P-matrices are restated, with slight modifications, for -matrices.