Some features of the unusual courtship behaviour of one of the world's rarest and most endangered species of bird, the flightless nocturnal Kakapo parrot of New Zealand, are described. They include excavation and maintenance by males of depressions or bowls which are grouped together and connected by tracks. Bowl systems occur in loose groups used by a number of males as traditional courtship areas and are unrelated to feeding or nesting. Bowls are used by males to emit resonant booming sounds that can be heard at distances of several kilometres, and for posturing and display in the presence of females when the latter visit for brief periods. It is concluded that absence of a permanent pair bond, the use of a mating station that is unrelated to feeding or nesting, and the temporally skewed sex ratio at the mating station in favour of males, all indicate that Kakapo are lek birds. They may be the only avian lek species to have evolved in an environment lacking mammalian predators. Further study of lek behaviour in the Kakapo may be needed if current efforts to save the species from extinction are to succeed.