At the London Congress in 1883 Sir Charles Dilke said that there were many people who knew a little about the Danube, but that there was not a single one who knew the subject thoroughly. This remark, and the fact that the Allied and Associated Powers have declared, in the various Treaties signed in Paris in 1919 and 1920, that they are to draw up a "General Conven tion" for the Regulation of traffic on the Donube and all other rivers declared international by those Trea ties, have encouraged me to write this work. As the subject is a very comprehensive one I have divided it into two parts. The first part deals very mi nutely with the :history of navigation on the Danube down to the year 1856. The second part contains fewer details, and is more in the nature of an outline, and covers the period from 1856 to the present day, and will form the subject of a later work. I have been very much indebted to Mr. Thomas W. Mc Callum, M.A., Lecturer at the University of Vien na, and Professor at the University of International Trade, not only for the great help he has given me in correcting this work, but also for his valuable informa tion and advice on numerous scientific questions. I also wish to express my sincere thanks to Sektions rat Dr. Bittner and to Dr. Fritz Antonius of the Court Archives in Vienna for all their kind help.