a b s t r a c tThis study deepens our knowledge of critical success factors in the innovation process of low-and mediumtechnology (LMT) industries. To accomplish this, it explores how the innovation process in LMT firms may depend on non-formal R&D activities and the use of external sources. The empirical analysis is based on a representative panel of Spanish manufacturing firms. The results strongly support the view that non-R&D activities such as design, the use of advanced machinery and training are crucial to understanding the innovation process of any firm. The study finds, however, that the impact of these activities is especially important in LMT industries, particularly for the achievement of product innovations. The empirical evidence also reveals the importance of external sources such as the use of consultants, the hiring of personnel, collaboration agreements and external R&D, with the greatest differences between LMT and high-technology (HT) firms being observed in process innovations.