The karyotypes of three species of cockatoos, Cacatua moluccensis, Cacatua goffini, and Cacatua sanguinea, and one Amazon parrot, Amazona aestiva, are described for the first time. These karyotypes are compared to the twenty-three species of psittacines published previously. Cacatua moluccensis appears to be a link in the evolutionary tree between Probosciger aterrimus and the other cockatoo species studied. This study reaffirms that the cockatoos are probably most closely related to the loris (Loriculus sp.) and Amazon parrots based on karyotype (M. W. M. Van Dongen & L. E. M. De Boer, (Genetica 65: 109–117) 1984).