This article is about border practices circumventing the law – "clandestine" migration, smuggling, psychotropics – and questions the function of border spaces. Indeed, when borders imply economic, legislative, and social disparities, they create their own economic opportunities outside of the legal frame. From the Hispanic-African border, I try to show how different populations seize on these disparities, how borders are diverted in favour of some people and to the detriment of others – most of them clandestine migrants – and, finally, how these crossings are in the heart of vast underground markets that are intermingled with official economic sectors. Thus, a question is posed about the socioeconomic specificity of border spaces.