One of the key assumptions in the original model of proto-industries, formulated by Mendels, Kriedte, Medick and Schlumbohm, is that the size and composition of families were determined by the proto-industrial work process in which those families were involved. The family was considered to be the basic unit of production, and the larger this unit, i.e. the more children a family had, the better. Among other reasons, with more children, a certain division of labour could be established within the family. However, later studies showed that there were many alternatives to the family as the unit of production, and that a division of labour could not only be established within families, but also between families. Families could take up other people into their households to perform proto-industrial work, or individual family members could perform specific tasks for merchant-entrepreneurs (the Verlagsystem or putting-out). Another option was for family members to perform specific tasks within the production process, by exchanging the required raw materials and intermediate products independently, either at periodic markets or through informal contacts with other producers. The latter option is the topic of this paper. The paper considers the division of labour in the Flemish linen industry around the 1840s, based on the linen censuses that were held in that decade. For many Flemish households at that time, the linen industry was a crucial part of their coping mechanisms. The production process encompassed several different steps that gave rise to a clear division of labour, which had regional and gendered dimensions. Firstly, the paper shows that periodic markets were a crucial element in enabling the division of labour in rural industries. In the 1840s, the linen industry of rural Flanders relied on a limited number of large markets for the sale of cloth, the final product, but also on a dense network of smaller markets where flax and yarn were exchanged. Trade at the latter markets was small, but the number of them ...