SUMMARYSaunders, D. A. 1977. Red-tailed Black Cockatoo breeding twice a year in the south-west of Western Australia. Emu 77: 107–110.The distribution of the Red-tailed Black Cockatoo in the south-west of Western Australia is shown. The breeding seasons of five species of cockatoo breeding in the Three Springs area are listed. All these species have winter-spring breeding seasons. The Red-tailed Black Cockatoo is the only species that breeds in the autumn as well. Breeding data for six female Red-tailed Black Cockatoos for the four breeding seasons from late 1974 to autumn 1976 are given. A survey of the literature shows the paucity of information on breeding seasons of the Red-tailed Black Cockatoo and the need for more detailed information throughout their range is pointed out.