Religious festivals in ancient Greece and Rome, where slaves were given a holiday or the roles of master and slaves were reversed, have been labelled ‘slave festivals’. This paper first highlights structural variations in different Greek slave festivals. Second, the function of the festivals is discussed, putting the previously suggested purpose as a ‘safety valve’ in the psychological framework of ‘coping factors’. It is argued that whereas slave festivals offering a holiday did serve as a ‘safety valve’, the festivals with a strict and temporary theme of reversal did not help with coping. The suggestion follows, that slave festivals served a religious function for the masters, balancing their good fortune against the slaves’ harsh fate.