The structural evolution of the films of an eutectoid Zn-Al based alloy was studied using X-ray diffraction, scanning electron microscopy and transmission electron microscopy techniques. The decomposition of nanophase eta'(n) was discovered to have started with clustering to form Z-zones and transitional phase, which was accompanied by an eutectoid decomposition, eta'(n) --> beta'(eut) + T'. The nanophase beta'(eut) appeared relatively stable during prolonged ageing at 220 degreesC. The stability of the nanophase stability is discussed by comparing it with the phase stability of the bulk microstructural alloy. The strongly preferred orientation at (1 1 1) crystal planes of the fee nanophase beta'(eut) considerably retarded the decomposition of the nanophase in the eutectoid Zn-Al based alloy films. (C) 2004 Elsevier B.V. All rights reserved.