The article argues that the notion of a 'religious market' is essentially a metaphor. It focuses analytic attention on certain aspects of the competition for allegiance among different forms of religion but at the expense of misrepresenting other core features. The attraction of the model for social scientists may well have as much to do with the normative character of the language of economic markets today as with the intrinsic analytic force of the model. The epistemological and ontological bases of the model are seldom examined though their implications are reductionist. The common use of the market model is also problematic in reinforcing the largely discredited, but still influential, assumption that the growth of Protestant 'fundamentalism' in developing societies is a function of American cultural and economic imperialism. The main body of the text examines the author's own selective use of the market metaphor in research on Latin American Pentecostals, highlighting both what is illuminated and what is distorted by the model. The discussion covers: the structuring of the religious 'market'; entrepreneurship, with particular reference to the pastorate; converts as 'clients' or 'customers'; the 'marketing strategies' of religious bodies; 'market niches'; and the 'pre-conditions of demand'. The article concludes that the market model tends to obscure the importance of the transformative processes in conversion. The market model should be employed with caution and without assuming its uniquely 'scientific' status as a methodological tool in the study of conversion and of the growth or decline of religion.