Chicken embryo manipulation, especially germline manipulation, recently has progressed greatly by devising important experimental techniques, such as embryo culture and primordial germ cell (PGC) manipulation. Embryogenesis and embryonic development in chickens are affected by gravity at various developmental stages. Freshly collected PGC population seems to contain germline-competent PGCs in opposite-sex germline chimeric chickens, but these PGCs probably disappear from the population during in vitro culture. Long-term culture of chicken PGCs makes it possible to transfer foreign DNA into the germline and also contributes to preserving avian genetic resources. Propagation of endangered avian species could become possible via interspecies germline chimeras. Development of techniques producing somatic cell-derived offspring could also be useful to avian germline manipulation.