This paper unravels the relations between different categories of the informal economy and their spatial distribution in the geographical setting of Brussels. Micro perspectives (households as economic agents) and macro perspectives (the informal economy related to economic recession) are combined in order to deal with categories of informal activities which are homogenous in terms of their spatial logic. In the first part we review several classifications of informal economic activities and assess them in terms of their congruence with the distinctions of economic actors and spatial logic. The second part elaborates on the raisons d’être of three large categories of informal economic activities in relation to urban development and on the production environments of these activities in Brussels: the domestic sector and suburban development; economic recession and survival strategies in the inner city; and, finally, flexibility and informalization in urban light industry. Polanyi’s concept of modes of economic integration (market, redistribution and reciprocity) offers a powerful tool to understand informal economic activities as a set of interrelations between households and other economic actors in order to gain access to their living resources