In this work, multilayered films-consisting of layers of self-assembled InAs quantum wires separated by InP spacers-were deposited on (0 0 1) InP substrates. We studied the vertical alignment of the nanostructures by using cross-section transmission electron microscopy (XTEM). A clear relation between the geometry of the wire cross-section and the stacking angles was observed. For asymmetric wires the stacking angle with respect to the growing direction is larger. Moreover, XTEM shows that the strain field generated by two nanowires can induce the nucleation of a unique wider nanowire in the subsequent InAs layer. Similarly to quantum-dot multilayers systems, this mechanism could produce uniform width distribution for the self-assembled nanowires. (C) 2003 Elsevier Science B.V. All rights reserved.