We present an efficient self-consistent method for the quantum transport of atomic-scale structures bridged between two metallic electrodes. It is based on the density-functional theory using the recursion-transfer-matrix (RTM) method with a separable form of norm-conserving nonlocal pseudopotentials. We did calculations with this method on the electric conductance of Al atomic wires with various kinds of a single atom mixed at the contact to one electrode. We found that the bonding nature of the atom at the contact significantly affects the transport properties. The bias drop in the atomic wire is strongly influenced by the local polarization of the atom at the contact. (C) 2004 Elsevier B.V. All rights reserved.