Demonstration of a high longitudinal stability of inter-individual diferences in behaviour has been one traditional goal of personality psychology. In recent years, impressively high longitudinal correlations have been reported for self-and other-ratings of behaviour in adulthood, indicating a high overall stability of personality differences in that period of development. However, even 5-year correlations around 0.70 do not exclude major deviations of some of the subjects from this overall stability (i.e. differential stability in the sample). Furthermore, the younger a sample is, the lower will be the longitudinal stability observed, and the less suficient is the explanation of inter-individual diferences by static traits. This article goes beyond the notion of stability at the sample level by asking from a developmental perspective (a) whether systematic inter-individual differences in intra-individual change exist, (b) how they can be assessed, and (c) whether these inter-individual differences can be explained by characteristics of the person or of the environment.