Few phenomena in the modern history of Asia can have been so completely misunderstood by Westerners as the Vietnamese religious (and political) movement known in European languages as ‘Caodaism’. Based upon a syncretic approach to religion, in which a key role is played by spirit-séances, it has inevitably been regarded by Christian writers with the same suspicion (if not contempt) as occidental ‘spiritualism’; and this initial lack of sympathy is compounded by the fact that the spirits who have revealed themselves at Caodaist séances include such familiar figures as Victor Hugo and Jeanne d'Arc. Then there is the show-piece temple of the Caodaists at Tây-Ninh, which drew forth Mr. Graham Greene's description of ‘Christ and Buddha looking down from the roof of the Cathedral on a Walt Disney fantasia of the East, dragons and snakes in Technicolor’. This superficial notion of the religious element in Caodaism fitted in very well with the cynicism of political observers, notably Bernard Fall, who saw in Caodaism no more than a political movement anxious to preserve its private armies and local power, using its religious ideas merely to dupe a credulous peasantry. In these circumstances, it is perhaps not surprising that the real nature and origins of Caodaism have been lost from view, and even its history has never been adequately summarized in any Western language. The present article will attempt to fill the historical gap, by tracing the history of the religion from 1925 to 1936, and then looking at its origins and antecedents. A subsequent article (to appear in BSOAS, XXXIII, 3, 1970) will analyse the various beliefs which have been incorporated into this essentially syncretic cult.