This article addresses the problem of exploring data for useful segments (and subsequently, market structure) in markets in which demand is a function of both consumer and situational characteristics. Current exploratory segmentation methods use either persons or situations as the unit of analysis, but not both. Yet choice and needs are frequently an unknown function of both personal characteristics and situational characteristics. Under these conditions of unknown strength of sources of influence, it may be advantageous to explore data. To allow the fruitful use of data exploration, we propose the use of a unit of analysis we call the person-in-situation, sampling of these units from their population, segmentation of these units with respect to choices, and the post-hoc exploration of such segments for regularities in individual and situational characteristics.