INTRODUCTION When in December 1960 the R.A.O.U. Checklist Committee was reorganised and the various tasks in hand were divided over its members, the owls were assigned to the author. While it was first thought that only the Boobook Owl, the systematics of which have been notoriously confused, would need thorough revision and that as regards the other species existing lists, for example Peters (1940), could be followed, it became soon apparent that it was impossible to make a satisfactory list without revision of all species. In this paper the four Australian species of Strigidae are fully revised, over their whole ranges, and the same has been done for Tyto tenebricosa. Of the other three Australian Tytonidae, however, only the Australian races have been considered: these species have a wide distribution (one of them virtually world-wide) and it was not expected that the very considerable amount of extra work needed to include extralimital races would be justified by results. Considerable attention has been paid to geographical distribution, and it appears that some species are much more restricted in distribution than has generally been assumed. A map of the distribution of each species is given; these maps are mainly based on material personally examined, and only when they extended the range as otherwise defined, have I made use of reliable field observations and material published but not seen by me. From the section on material examined it will be easy to trace the localities; where other information has been used, the reference follows the locality. ACKNOWLEDGEMENTS The revision was carried out, besides the Western Australian Museum,