This paper aims to stimulate interest in the early micro-economic conceptualisation of housing submarkets proposed by Rapkin and Grigsby, which defined market areas in terms of dwelling substitutability. Three key questions need to be addressed if a return to the Rapkin–Grigsby approach is to be achievable and worthwhile. First, what are the practical benefits? (The paper highlights a range of potential research applications that would benefit from the substitutability approach.) Secondly, in what way are existing approaches likely to be inadequate for demarcating substitutability-based submarkets? (Four criteria are proposed for assessing submarket estimation methods which existing approaches fail to satisfy.) Thirdly, what are the prospects for developing a substitutability metric that will make the Rapkin–Grigsby definition empirically feasible? (A new measure is proposed, based on the cross-price elasticity of price (CPEP), which is illustrated using data for Glasgow, Scotland.)