The following paper attempts to fix the position of the house or houses of Augustus on the Palatine and of the temple of Apollo Palatinus. In the enquiries which led up to it, I have to acknowledge effectual help from Miss E. Van Deman, Dr. T. Ashby, Mrs. Strong, Mr. H. Stuart Jones, Professor Giovanni Pinza, author of a theory from which I have appropriated much, and last, but not least, Commendatore Boni and his assistants. Sr. Moggi, Mr. F. G. Newton, and Mr. J. W. Rodger of Cardiff have contributed the plans which accompany this paper.