The retroviral oncogene v-myb encodes a transcription factor (v-Myb) which is responsible for the ability of avian myeloblastosis virus (AMV) to transform myelomonocytic cells. v-Myb is thought to disrupt the differentiation of myelomonocytic cells by affecting the expression of specific target genes. To identify such genes we have analysed the gene expression in a myelomonocytic chicken cell line that carries an estrogen inducible version of v-Myb by differential display. Here we describe the identification of the chicken homolog of the mouse Pdcd4 gene as a novel v-Myb target gene. Pdcd4 is also known as MA-3, TIS and H731 and has recently been shown to suppress the transformation of epidermal cells by tumor promoters. Our results provide the first evidence that v-Myb directly regulates the expression of a potential tumor suppressor gene.