The methods and applications for using avian replication-competent retroviruses to target gene misexpression in the developing limb bud of the chicken are described. These viruses provide the means to exploit the strengths of the chick as a model system in experimental embryology in conjunction with a genetic approach for ectopically expressing a gene of interest. The applications and strengths of the system are detailed. All the steps required to produce a virus carrying a transgene of interest and the methodologies behind designing and carrying out misexpression strategies are outlined, and some useful techniques for analyzing infected embryos are described.