In this paper, the determinants of exit to foreign markets among small and medium Spanish manufacturing firms are analysed. Departing from a simplified model which remarks the importance of exit costs, the traditionally considered variables of a set of non-exporters in 1990 are related to the firm behaviour in 1995 in order to avoid simultaneity between them. The results show that technological activities, staff qualification, size, labour productivity and access to specialised intermediaries are the main determinants of becoming an exporter for these firms.