This paper attempts to interpret the interrelated dimensions of learning between technological professions (technicians, engineers, researchers) and the dynamic process of innovation on the basis of a international comparative analysis. One of main hypothesis is that scientific and technological professions, far from constituting a universal and homogeneous category, are "social constructs" which embody a specific mode of knowledge creation in Japan and France and thus tend to structure national patterns of innovation. On the basis of our Franco-Japanese comparative research (three couples of firms in the chemical, the electric/electronic and software service sectors), we focus our analysis on some facts in the construction of the engineer category which offer sharp contrasts from one country to another: a clear difference in the way engineers in France and in Japan are certified by higher education systems; a difference in the way their career patterns (mobility, training, incentive system) are organised. The nature of innovative capacity seems finally to be closely linked to the way that the career patterns of engineers/scientists are managed, at both the national and the firm level, in order to create the linkage between individual leaning and the collective accumulation of knowledge.