This article analyzes the profile of individuals who have undertaken clandestine work, and their motivations for doing so. It also enquires into the particularities of clandestine work as compared to declared work, and the relatively improved future employability of those who resort to it. Although diverse, the biographies of these people often feature struggles and gaps in education and professional life. Clandestine work provides income and allows them to maintain a self-image often threatened by professional uncertainty. Apart from the absence of declaration, clandestine work is similar to declared activities in terms of work organization. There are four recurring justifications for clandestine work. The first presents it as a strategy for modifying a rule that is judged to be too strict. The second presents it as an informal service within a network of individuals. In the third case, individuals explain that clandestine work allows them to develop new kinds of skills, different from the ones they use in their everyday job. The fourth justification is that of a demonstration of individual responsibility: clandestine work allows individuals to avoid recourse to social assistance.