A method for analysing the localization of the Hox-4 gene complex by three-dimensional reconstruction of serial cross-sections is presented. It allows the simultaneous visualization of three Hox expression domains on the same reconstructed embryo and the study of the effect of a graft of chicken polarizing region on the de novo expression of the genes of the HOX-4 complex. The method consists of registering the sections, segmenting the biological patterns and finally displaying the reconstructed embryo. The precise relationships between the transcript domains of the three genes can thus be assessed in either the normal wing bud or upon pattern modification