This chapter addresses the question of how people change as a consequence of occupational experience. We are concerned specifically with the impact of changes in work role on individuals. Role change is a characteristic feature of organizational life. At any point in time many individuals will be in the process of changing their job, moving either between or within the same organization. This is not a new phenomenon, although, arguably, the rate of change in working lives has been accelerating steadily in recent decades (Alban-Metcalfe 1984; Nicholson 1984). In view of its importance both for the people who move and for the organizations within and between which mobility occurs, it is surprising that only in the 1980s has the study of career transitions come of age as a field of inquiry (Allen and Van de Vliert 1984). This status can be claimed for the area because it raises distinctive theoretical and practical questions that do not figure in the related literatures on turnover, vocational choice, or lifelong career development which hitherto have dominated the literature on occupational mobility. These questions arise when one shifts the focus down from the level of the lifespan of the organization, to scrutinize the particular qualities of individual experience of change. This opens up the way for theory building about how consequences of job change may depend on identifiable features of the transition.