Research into the relationship between housing and health has frequently been narrowly focused, fragmented, and of marginal practical relevance to either housing or health policy. From an extensive review of the literature, this paper reports on the current state of knowledge about the relationship between housing and health. The research falls into four distinct categories: (1) specific physical or chemical exposures; (2) specific biological exposures; (3) physical characteristics of the house; and (4) social, economic, and cultural characteristics of housing. Much of the general literature on the effects of housing on health cites previous studies and then proceeds to advocate housing policies and strategies that are aimed at improving population health. Studies providing original data on the relationship, which is the vast majority of the literature, focus on very specific physical, chemical, and biological exposures with a known or suspected effect on health within the house, or they focus on the social, economic, and cultural characteristics of the house. The mechanisms through which specific aspects of housing affect health are extremely complicated, but they do exist. Researchers have made a great deal of progress in clarifying some of these mechanisms. A large gap still exists in our knowledge about the links and pathways between housing, socio-economic status and health status.