Self-determination theory is a theory of personality and motivation that provides a perspective on the social-cognitive dimensions that underpin human behaviour. According to self-determination theory, there are three basic psychological needs that are universally fundamental for self-motivation and psychological well-being. The hypothesis of universal needs suggests that, when satisfied, autonomy, competence and relatedness are equally beneficial for all people, regardless of any potential individual differences in need strength (cf. Deci & Ryan, 1985; Ryan & Deci, 2002). However, other theories developed within personality and social psychology tend to view needs as learned and varied (e.g., McClelland, 1985; Murray, 1938). As such, there is some debate as to whether the needs described by self-determination theory are universal requirements, or whether they are learned dispositions that vary across individuals (Sheldon & Niemiec, 2006). Sense of coherence theory (Antonovsky, 1979; 1987) is another perspective on psychological health and well-being. The core dimensions of sense of coherence appear to share some similarities with self-determination theory. However, the theories have different traditional foci. Research in sense of coherence theory is traditionally concerned with how a person survives despite the chaos and stress of life (e.g., the absence of ill health). Conversely, empirical research in self-determination theory has historically focused on how basic need satisfaction facilitates positive psychological well-being and growth orientated behaviour. Because of the difference in traditional foci, research within the framework of sense of coherence and basic needs satisfaction has taken place independently. As such, the relationship between the two theories and associated well-being is yet to be addressed. Chapter 1 outlines the theoretical rationale on which the empirical chapters are based. Chapter 2 of this thesis provides evidence that the benefits of need satisfaction are not always equal; rather, they are dependent on their relative intra-individual importance. Studies 2 1, 2 and part one of Study 4 show that the motivation benefits associated with need satisfaction gained via a specific activity depend on intra-individual differences in need importance. Studies 3 and part two of Study 4 show that for the general population, the effects of need satisfaction on general well-being are equal for all people regardless of the importance attached to each need. Those data support Deci and Ryan’s (1985) universal benefits position. However, Studies 1 and part one of Study 4 show that when an individual’s sense of identity is highly related to their investment in a specific activity, the association between need satisfaction (via an important activity) and general well-being depends on the intra-individual level of need importance. Those data counter self-determination theory’s universal benefits position. Collectively, these findings support the position that self-determination theory’s basic psychological needs are not always universally required for motivation and well-being. First, Chapter 3 (Study 5) provided support for the credibility of a four-factor sense of coherence scale, with an additional dimension, termed relationality. Second, Study 5 provided evidence for a considerable conceptual overlap (60%) among the dimensions of sense of coherence and basic needs perspectives. Third, in a series of longitudinal mediation analyses, satisfaction of basic needs significantly mediated the relationship between sense of coherence and positive well-being, but failed to mediate the relationship between sense of coherence and the absence of psychiatric symptoms. In addition, those analyses showed that sense of coherence was directly associated lower levels of psychiatric symptoms. Collectively, these findings are in line with the origin of both theories, and suggest that the dimensional structure of sense of coherence more adequately explains the absence of psychiatric illness than basic need satisfaction, whereas basic need satisfaction only explains the presence of positive psychological well-being. Chapter 4 of this thesis discusses the results from the two experimental chapters (Chapter 2 and 3) in a broad theoretical context.