A survey of the historical and religious problems involved in the interconnection between the Sabians of the Qu'ran, the Mandaeans of southern Iraq, and the `Sabians' of Harran in northern Mesopotamia. This is the third in the new series of Supplements to the Journal of Semitic Studies (OUP). These supplements will be published in hardback and sold as books: they will not be available as part of the subscription to the Journal.