Identifying the gene expression alterations that occur in both the tumor and stroma is essential to understanding tumor biology. We have developed a dual-species microarray analysis method that allows the dissection of both tumor and stromal gene expression profiles from xenograft models, based on limited interspecies cross-hybridization on Illumina gene expression beadchips. This methodology allows for simultaneous genome-wide analysis of gene expression profiles of both tumor cells and the associated stromal tissue.