Commuting has become a much discussed policy issue in Ireland, as a consequence of a significant increase in the number of commuters and car users and the resulting increase in congestion. Despite this interest in commuting there has been little research on the causes of the increase in commuting and the pattern of commuting. This paper proposes a simple framework which links the decision of individuals to commute with the housing market, the labour market and commuting costs. Furthermore this paper investigates the empirical validity of the main predictions of this simple framework using a new data set on inter county commuting flows. The findings of the empirical analysis offer support for the analytical framework. Thus, relative wages and relative house prices between counties are important factors in determining commuting choice.