The goal of this thesis was to define the nature and outcomes of Australian professional supervision by applying Holloway's (1995) Systems Approach to Supervision (SAS) across professional groups. Many Australian professionals such as psychologists, counsellors, and accountants are required to participate in some form of supervision before being granted permission, via registration, to practice independently within their respective fields. This is the first study of its kind to investigate the supervision experience of a range of professional groups within Australia. The SAS model (Holloway, 1995) provided a well-researched theoretical and practical framework with the potential to be applied across professional groups for the purposes of developing, evaluating and enhancing supervisor and supervisee practice. Based on the model, Holloway proposed a number of teaching tasks and functions in a matrix to explain the process of supervision and to assist in the professional and personal development of supervisees. To date, most of the literature on professional supervision has failed to provide a theoretical framework from which results could be meaningfully interpreted. This thesis outlines a program of research which used the SAS model as a theoretical basis for understanding and evaluating the experience of supervision amongst a range of Australian professional and its relationship to effective professional practice. Four studies were conducted in accordance with Mackenzie and House's (1979) Model of Scientific Inquiry. The first study (Study One) was exploratory in nature, and aimed to define the term "supervision" and the anticipated outcomes of supervision activities. The second study (Study Two) was also exploratory in nature, and aimed to evaluate the modes of supervision delivery as well as to collect information regarding the key tasks and functions utilised in professional supervision. The third study (Study Three) was empirical in nature, and investigated the supervision experience of psychologists engaged in supervision in accordance with the SAS model (Holloway, 1995). It longitudinally tracked their performance over a 12-month period as evaluated by both their supervisors and work managers. The fourth study (Study Four) was confirmatory in nature, and was the same as the third study but comprised a different sample of business and accounting (who were not Certified Public Accountants) graduates. The four studies consisted of four separate samples surveyed with self-report measures developed from the SAS model (Holloway, 1995) by the researcher. Study One comprised a sample of 210 supervisor-supervisee dyads. Professional groups in this sample were psychologists, counsellors, nurses, occupational therapists, financial advisors, business consultants, and accountants (without CPA) all of whom were participating in a supervision process. Study Two comprised a total of 200 supervisees broken down into four groups of 50. The professional types included in this sample were psychologists, counsellors, nurses and business consultants and accountants (without a CPA). Study Three comprised 513 supervisees who were participating in supervision as part of the criteria to become fully registered psychologists. Study Four included 480 business consultants and accountants (without CPA) who were in the early years of their career and were participating in supervision as part of their professional development. The central aims of the supervision experience, according to supervisees and supervisors, were to develop skills in counselling, case experience, professional experience, emotional awareness, the ability to self-evaluate and network. The six reported outcomes of supervision were that professional supervision enhanced supervisees' ability to self-evaluate, gain academic knowledge, become emotionally aware, develop profession networks, develop both professional and work skills and to build on relationship skills. The findings supported and extended the SAS model (Holloway, 1995) by adding the tasks of academic knowledge and networking. The definition of supervision found in this research program also supported and built on the definitions already provided in the literature. There was considerable support for the SAS model's matrix in that particular supervision functions employed to teach certain supervision tasks were more effective than others. For example, on the one hand, to teach a supervisee the skill of emotional awareness, a supervisor is best advised to take a supportive/sharing approach. On the other hand, it was shown that the teaching strategy of monitoring/evaluating was not found to be conducive to teaching case conceptualisation skills. The findings also suggested two enhancements to Holloway's original conceptualisation of the SAS model of supervision delivery mode and supervisor allocation. Furthermore, the findings confirmed that the SAS model can be applied to teach and objectively evaluate supervision success by supervisors and managers across professional groups. There were six major contributions of this research program to the field of professional supervision: First, there was the application and validation of a theoretical model, Holloway's (1995) Systems Approach to Supervision, to the supervision experience. Second, there was the development and application of scales to measure supervision performance and satisfaction reliably and with demonstrated construct validity. Third, the methodology which included the collection of both qualitative and quantitative responses from supervisees, supervisors, and managers provided a multi-method approach to understanding professional supervision across professional groups. Fourth, a uniform definition of supervision was identified across a range of professional groups. Fifth, Holloway's supervision teaching matrix was empirically supported and the findings recommend it as a mechanism for developing, evaluating and enhancing supervisor and supervisee practice across a range of professional types. The SAS model was found to be relevant to health-related professional groups but also supported in business-related professional groups. Finally, the research recommended some modifications to the SAS model to incorporate factors such as supervision delivery mode. These additions and the results of the longitudinal research suggested that supervision effectiveness was a predictor of on the job performance ratings by managers. Based on a scan of the literature to date, this research program outlines the first longitudinal empirical study of the relationship between supervision effectiveness and on-the-job performance using a range of professional groups. Limitations and future directions were discussed.