The importance of followers in leadership and organisational outcomes is increasingly being recognised. While traditionally seen as those who enact the directions of leaders and thereby enable organisational goals to be achieved, followers have more recently been reconsidered as partners in the leadership process with mutual influence characterising follower-leader relationships. As there can be no leaders without followers and vice versa, it is not possible to effectively study one without the other. This thesis argues that for the field to progress meaningfully, following and leading must be conceptualised and defined to make clear how they are distinctive and yet interrelated behavioural processes. Such definitions, when operationalised in research, hold promise of improved construct validity that is much needed in the field (Bedeian & Hunt, 2006). Such definitions also make possible the investigation of a key research question directing this thesis: Why do followers follow? The answers to this question may provide crucial insight into the leadership process, thereby advancing the field. Three studies are reported. The first study, a systematised review of empirical followership research from 1955 to 2017, sought to answer three questions: What is known about followers, following, and the role of followership in the leadership process? What empirical support exists for followership theories? What direction should future research take? Two hundred and eight published studies and 89 unpublished studies (N = 297) were reviewed to draw three main conclusions. First, leadership was shown to be a socially constructed process in which followers have agency and impact. Second, research investigating the reasons for follower compliance with leader direction is minimal; and third, there appears to be a disconnect between followership theory and empirical evidence. In addition to these conclusions, an emerging proposition was identified: organisational members, regardless of subordinate or superordinate status, engage in both leading and following. This proposition represents a second paradigm termed follower-leader switching that sits alongside the role-based paradigm, which dominates the field. Building on findings from Study 1, the essence of leading was determined to be influence, and the essence of following was conceptualised as compliance (deferring to others). These concepts informed the operationalisation of follower and leader acts for both Studies 2 and 3. Study 2 addressed a gap identified in the literature by seeking to answer the question of why followers follow. This study involved the systematic development of a reliable 7-factor Reasons for Compliance Scale, using data from a heterogeneous sample (N = 438). The scale provides insight into the psychological triggers behind decisions to comply with (follow) workplace requests. This knowledge seems new and, as far as can be ascertained, there exists no other measure of reasons for compliance with workplace requests. The Reasons for Compliance Scale was used in Study 3. Study 3 explored the essence of follower-leader interactions using fieldwork. It aimed to build on findings from Study 1, particularly the limited empirical support for followership theory and measures, and further test the scale developed in Study 2. The overarching research questions were What are the relationships between follower and leader behaviours? and How are follower-leader behaviours related to organisational climate? Multiple theories informed the design of Study 3, with field theory (Lewin, 1943) forming the overarching meta-theory. The mixed methods research was conducted in three large Australian public secondary schools. It involved naturalistic observations of leader–follower interactions, one-on-one interviews with 14 school personnel, questionnaires completed by 64 additional personnel, and the use of archival records. In addition to testing a newly developed follower-leader switching model (FLSM), the Reasons for Compliance Scale, and the manner of compliance (e.g., conscientiously or reluctantly) measure, Study 3 examined the role of influence tactics, social identity, and the length of dyadic relationships in follower-leader dynamics. Findings included positive correlations between climate and each of (a) the influence tactic of inspirational appeal, (b) positive manner of compliance, and (c) the compliance trigger of features of the dyadic interaction. Data trends indicated positive associations between follower-leader switching and both school climate and social identity. The contributions of this thesis are potentially many. In addition to building and testing theory, the project has delivered tools in the form of concepts, frameworks, and measures that may have practical value or guide future research. Overall, this thesis has shown that the study of followership cannot be divorced from the study of leadership, or vice versa, and that followership should not be investigated separately from macro (e.g., climate), meso (e.g., social relationships), and micro (e.g., cognitive/affective/motivational states) phenomena. Future researchers are encouraged to use integrated follower-leader models and multiple methodologies to enhance understanding of followership and related organisational processes and outcomes.