Enterprises are a key provider of education and training for adults across OECD countries. Yet, policy-makers lack a detailed understanding of how training in enterprises takes place. This report opens the black box of training and informal learning in enterprises by providing in-depth insights on: i) what training and learning opportunities enterprises provide; ii) why they provide training (or not); and iii) how they make decisions about training. It presents new evidence from 100 qualitative cases studies in five countries: Austria, Estonia, France, Ireland and Italy. The findings will assist governments and social partners in designing and implementing better policies in support of training in enterprises.