An action theoretic account of skill learning and skill use is offered as a useful heuristic for life-span developmental psychology. It is suggested that analyses of the tasks confronting an individual and of the structure of action, as well as of the interplay of these two, have implications for the understanding of development across the life span. In particular, these analyses have implications for the disuse hypothesis, the issue of stability and cross-situalional consistency of behavioral dispositions, the issue of the degree of awareness of action strategies, and the understanding of so-called skill traps. Furthermore, the concept of stage can be conceptualized differently within this framework. Finally, action theory, with its emphasis on the task structure, is able to circumvent the subjectivistic concepts which plague analyses of behavior, without giving up the principle that individuals actively structure their cognitions and their environments. © 1984 S. Karger AG, Basel.