Although there appears to be considerable popular interest in workaholism, scientific understanding of the construct is very limited. Paradoxically, although many argue that the personal cost of workaholism to workers, families and friends is enormous, these people’s perspectives do not appear to have been analysed using formal scientific paradigms (Scott, Moore, Miceli, 1997). The present research considers the construct of workaholism in its impact on people’s lives. The thesis comprises six chapters that outline data from three separate studies. The theoretical perspective involves interaction theory, where workaholism is hypothesised to arise from a personal tendency toward workaholic behaviour that is activated and maintained by reinforcing stimuli. The epistemological perspective involves applied research in a naturalistic setting, using triangulated, quantitative data within a contrasted-group design (i.e., workaholics, non-workaholics). Time diaries were used to assess the impact of workaholism on the allocation of time to ‘outside-work’ activities such as sleeping and exercising. Together, the data validated the two-factor measure of workaholism, corroborated the theoretically based definition, and showed that workaholism was distinct from four generic ethics (work, achievement, leisure, and time) and three specific constructs (obsessive thinking, compulsive finishing and delayed gratification). Workaholism scores were stable across time and held a consistent temporal relationship to work and leisure behaviours and intrapersonal and interpersonal well-being. Additionally, while workaholics evidenced differing work and leisure patterns to non-workaholics, they experienced similar health status, pleasure and relationship satisfaction. Thus, workaholism impacted on peoples’ choices about time allocated to work and non-work activities, but it was not necessarily harmful. These data are congruent with interaction theory, support the inductively generated definition of workaholism, and thereby provide a conceptual springboard for evolving future research designs. In sum, the research advances contemporary knowledge about workaholism in five ways (a) by providing one of the first systematic analyses of workaholism using data from multivariate sources, (b) by generating longitudinal New Zealand data from contrasted groups, (c) by analysing significant others’ perceptions of workaholism, (d) generating an empirically based operational definition, and (e) by adapting innovative measurement methods from other fields (e.g., time diaries) for use in workaholism research.