Four longitudinal models are used to present a short review of research into adolescent psychosocial development. This review reveals adolescent development to proceed in a regular manner. This process of regular development suggests that it might be possible to uncover rules of intra-individual development. The aim of this paper is to propose a framework of such rules. The framework starts from three propositions of life-span psychology: (1) development has a direction; (2) development is multidirectional; (3) there is plasticity: within-person variability in development. The first proposition leads to the distinction between normative endpoints and transient states. The second proposition unfolds in the distinction between equifinality and multifinality and the notions of developmental neighbourhood effects, developmental continua and frequency of change. The third proposition shows changes in the prevalence of normative endpoints. Application of the framework to research into adolescent psychosocial development shows it to be useful to describe intra-individual development in a systematic manner.