Purpose - The purpose of this paper is to enrich the discussion on the determinants of training participation and informal learning of scientists and engineers (S&Es). Design/methodology/approach - Tobit analyses on survey data. Findings - The authors find that both formal training and informal learning are particularly related to job and firm characteristics instead of labour supply characteristics. S&Es employed in firms that apply innovative production processes more often participate in formal training, and also benefit from the informal learning potential of their jobs. However, lifelong learning is not triggered in firms with many product innovations. S&Es who are employed in firms that operate on highly competitive markets also participate in formal training less often. The same holds for S&Es employed in small firms, although the latter compensate this by more hours of self-teaching. S&Es employed in jobs that require a high level of technical knowledge more often participate in formal training, whereas those employed in jobs that require more general skills are more involved in informal learning. Furthermore, older S&Es with long firm tenures participate in formal training less often, and have fewer opportunities for learning in their jobs. Therefore, their competence level is at risk. Practical implications - Public policies. that stimulate process innovation also appear to prevent skills obsolescence among S&Es. Public policies that aim to diminish labour market shortages of S&Es by discouraging early retirement should particularly take account of the necessity to keep the human capital of older S&Es with long firm tenures up to date. Originality/value - The paper contributes to the literature on the determinants of human capital development by including both formal training and different modes of informal learning; and employee characteristics as well as job and firm characteristics in its analyses.