This study examines the contrast between Muslim reproductive attitudes and behaviour in Thailand and those of Buddhists, especially in the southern region. Results are based primarily on a large regional survey directed towards this topic and focus group discussions among Muslims in Southern Thailand. We interpret Muslim reproductive patterns from the perspectives of the major hypotheses that have been invoked in the social demographic literature to explain links between religion and fertility. These hypotheses partly explain what appears to be a complex and context-specific relationship. Nevertheless, the linkages between religion, ethnic and cultural identity, and political setting that appear to operate are more complex than can be fully explained by even a combination of the existing hypotheses.