This study concerns the relationship between organisational and professional commitment over time. The study was conducted among solicitors In large commercial practices. Reviewing the literature on organisational and professional commitment three issues appeared salient. The first concerns the extent to which commitment Is time related. The second concerns the extent to which professional and organisational commitment are compatible. The third relates to the nature of commitment. Levinson's (1978) theory of adult development provided the framework of analysis for the present study. The core of Levinson's theory Is that people experience periods of stability and transition during their lifetime. Moreover, these changes are to some extent predetermined. The present study tests the Idea that commitment generally Increases with age. The underlying assumption is that older people are generally more satisfied with life In general than younger people. Another set of hypotheses relates to the relationship between organisational and professional commitment. It Is expected that both forms of commitment are complementary. Levinson suggests that at each life structure individuals experience different Intensities of commitment. This Is shaped by personality development as well as the processes of adaptation and socialisation. Finally, the motives behind an Individual's decision to stay In the organisation or the profession determines the nature of their commitments. It Is expected that professionals express their commitments In terms of a positive attitude rather than Instrumental behaviour. Organisational and professional commitment were measured using Meyer and Alien's (1991) scale.The measuresof organisational and professional commitment differentiated between attitudinal and behavioural dimensions. Attitudinal commitment was defined as the psychological Identification and attachment to the firm and to the profession (affective commitment), as well as a perceived moral duty to remain In the firm and profession (normative commitment). Behavioural commitment wasdescribed aspersonal sacrifices and the costs of quitting either the profession or the firm (continuance commitment). The survey also measured Job Involvement (Lodahl and Kejner 1965). professionalism (Hall 1968), and work values orientation (Shepard 1972; Popper and Lipshizt 1992). A sample was drawn randomly from large solicitors' firms In London, Birmingham, Leeds and Manchester. 403 usable replies were received. Data were analyzed mainly by t-test and Oneway Analysis of Variance (A.N.O.V.A) and Duncan's multiple-range test for multiple comparisons. The results confirm the Initial hypotheses. Age was found to be a stronger predictor of commitment than Individuals' experiences. Further, solicitors are more professionally than organisationally committed. This finding Is, however, subjected to some qualifications. The sense of 'wanting to stay' and 'needing to stay' Is higher for the profession than the firms. Yet the 'obllgation to stay' Is higher for the organisation than the profession. When results are analysed by age, professional commitment predominates only among solicitors In the early career stage. Thereafter, no form of commitment predominates until 'Mid-life Transition'. At this stage, organisational commitment predominates. In the late career stage, there Is no significant difference between both forms of commitment. Generally, affective commitment predominates over calculative commitment. The theoretical and practical Implications of the findings of the present study are discussed. The thesis Includes suggestions for future research.