The localization of a neuron-specific β-tubulin isotype in the ultimobranchial glands from chickens at various stages of development was studied by means of light- and electron microscopic immunohistochemistry with a monoclonal antibody (TuJ1) against the β-tubulin isotype, cβ4. At 8 days of incubation, many C cells in the ultimobranchial glands showed immunoreactivity for TuJ1 in variable degrees, weak to intense. At 12 days of incubation, a vast majority of C cells were intensely immunoreactive for TuJ1, and further TuJ1-immunoreactive nerve fibers were distributed in the ultimobranchial glands. At 14 and 16 days of incubation, intense immunoreactivity for TuJ1 was sustained in the C cells. Electron microscopic analyses revealed that TuJ1 immunoreactivity was diffusely distributed throughout the cytoplasm and also localized on the secretory granules of C cells at these stages. TuJ1 immunoreactivity in the C cells started to decrease at late stages of embryonic development. At the hatching period, dense distributions of TuJ1-immunoreactive nerve fibers were observed in the ultimobranchial glands, whereas TuJ1 immunoreactivity of the C cells became very weak. In 10-day-old chickens, TuJ1 immunoreactivity was restricted to the nerve fibers.