The paper looks at the development of new forms of employment (or "atypical jobs") in Italy, in particular at the case of Collaborators, semi-independents contractors who stipulate fixed term contracts, and at the social mechanisms that regulate them. The behaviour of labour demand and labour supply will be contextually analysed. In fact, since with this kind of form of employment the institutional regulation is nearly absent, Collaborators and employers move in a situation of uncertainty, in which there is the possibility of opportunism from both the sides of market. So, the hypothesis is that the problematic aspects of this form of atypical job are solved through social mechanisms as reputations, closure of networks. The paper explores these mechanisms. The empirical data come from a qualitative analysis, based on partially standardised interviews to employers and employees, which has been conduced in the area of Turin (Piedmont, Italy) between February and March 2000.