In this article, I compare women's work opportunities in Bilbao, in northern Castile, and Antwerp, in the Low Countries, from 1400 to 1560. I argue that the different organisation of work in the two towns had a great influence on women's economic opportunities. Whereas women in Antwerp often worked alongside other members of their household because of the town's dominant craft guilds, Bilbao's informal trades were open to women on their own, independent of their husband or another male relative. As a result, women in Bilbao are more visible in the sources and were able to exert more influence on the town council.