Private supplementary tutoring has long been a major phenomenon in parts of East Asia, including Japan, Hong Kong, South Korea and Taiwan. In recent times it has grown dramatically in other parts of Asia and in Africa, Europe and North America. The factors underlying the growth of private tutoring vary, but in all settings it has major implications for learning and livelihood. Families with the necessary resources are able to secure not only greater quantities but also better qualities of private tutoring. Children receiving such tutoring are then able to perform better in school, and in the long run to improve their lifetime earnings. By contrast, children of low-income families who do not receive such benefits may not be able to keep up with their peers and may drop out of school at an earlier age. Tutoring also of course has a direct impact on the livelihoods of the tutors, providing employment and incomes for a range of professionals and amateurs of different age groups. The dynamics of inter-relationships are complex, and vary from one setting to another. This paper argues that private supplementary tutoring deserves much more attention from policy makers and researchers. (Contains 1 table.)