Rous sarcoma virus (RSV)-derived retroviral vectors have allowed for efficient gene transfer into the chicken embryo which is a classical model for studying vertebrate development. Current evidence reveals that this method can be used for regionally restricted expression, inducible expression, and for interfering with endogenous gene function, suggesting that gain-of-function and loss-of-function strategies for specific genes can be achieved spatially and temporally in the avian embryo. Thus, retroviral-mediated gene transfer into the chicken embryo coupled with a wide variety of strategies is now an important tool to address specific biological questions in the vertebrate.