The characterization of cell behavior in quail chick chimeras has greatly increased our knowledge of the ontogeny of embryonic cell populations and the role of cell-cell interactions in development. We sought to extend the value of avian chimeras by producing a marker that would recognize cell surface components and that could be used instead of the traditional nuclear marker to identify quail cells within chimeras. We describe here a quail-specific antiserum produced by injecting chickens with a membrane fraction of 6-10-day quail embryos. By use of peroxidase coupling of a second antibody, serum reactivity was tested in tissue sections of normal quail and chick embryos and of somitic mesoderm and neural tube chimeras. The primary time period examined was 6-10 days of development. At these stages, the antiserum recognizes only quail cells and stains both plasma membrane-associated and cytoplasmic cell components. The latter characteristics allow the identification of quail axons in chimeras and facilitate visualization of quail cells at low magnification. We show that antiserum staining can also be used to identify quail cells in culture and can be combined with orthograde HRP labeling of neurons.