We denote by $mathcal{Q}$(A) the set of all real matrices with the same sign pattern as a real matrix A. A matrix A is an SN-matrix provided there exists a set S of sign pattern such that the set of sign patterns of vectors in the -space of $ ilde{A}$ is S, for each ${ ilde{A}}{in}mathcal{Q}(A)$. Some properties of SN-matrices arc investigated.