The offshore oil and gas industry has created significant wealth for the UK economy; approximately 250 billion Great British Pounds (GBP) since oil was discovered under the United Kingdom Continental Shelf (UKCS) of which approximately 70 billion GBP was paid in tax and royalties to the UK government. The industry currently employs about 35,000 individuals directly and supports many more jobs indirectly. In short, it is a very critical industry to the UK economy. But for all its contribution, there is a dearth of social science and management research into the how the offshore industry is managed. This thesis reports the background and findings of an investigation into the first level of the platform production management team and examines this role in terms of the personal characteristics and man-management skills required within this working environment. This thesis was the first study that attempted to investigate the non-technical characteristics of high performing supervisors. It examined the question of what makes an effective supervisor in terms of biodata, personality, job satisfaction and perceptions of the work environment. The transformational model of Bass and Avolio (1990) was also adapted to assess leadership style. A specially designed semistructured questionnaire was developed. The research sample comprised of one hundred first line supervisors (operators and contractors), their subordinates and their superiors on three North Sea platforms. It was hypothesised that effective offshore first line supervisors would have a distinct supervisory style compared to less effective ones. Other aims included assessing the differences between supervisors working on the UKCS and those on the Norwegian Continental Shelf (NCS); and between supervisors working for contracting companies as opposed to operating companies. The key contributions of the thesis were in the following four areas; (i) the summary data that described the offshore first line supervisors, (ii) the findings from standard instruments, particularly the Bass leadership instrument, identified that supervisory effectiveness was dependent on the platform membership of the supervisor, (iii) the qualitative findings from the supervisory decision making vignettes and finally (iv) the platform differences that were elicited from both within the UK sector and between the North Sea sectors. For example, on one UK platform, UKI, the more effective supervisor displayed a more transactional leadership style, namely taking an active role in enforcing workplace standards. There was some evidence to suggest that dimensions of a transformational leadership style such as motivating subordinates through pep talks and depicting visions of a better workplace were positively correlated with performance. These findings were broadly consistent with the results of previous research. In contrast, the second UK platform, UK2, produced a different finding. This was surprising given the numerous physical and organisational characteristics that these two platforms had in common. The Norwegian platform sample was small (n= 19) and therefore correlational results were largely exploratory. Further differences were revealed through multi-variate analyses between all three platforms based on leadership, job satisfaction and biodata variables. This implies that `effectiveness' may be dependent on the platform membership of the supervisor. As an alternative explanation, these findings may suggest that the standard instruments and appraisal measures were not sensitive enough to differentiate performance within this work environment. The Bass and Avolio (1990) leadership model, in particular, produced contradictory findings and its usefulness in this context remains questionable. Qualitative evidence from the total sample of effective supervisory behaviours, using a behavioural event interview method, supported the quantitative findings from UK1 but broadly disagreed with the findings from UK2. Measuring supervisors performance without reference to objective indices remains a weakness for this style of research. The impact of these findings is discussed in the context of both practical recommendations for recruitment, selection and development for the supervisory population and future research into management research in the offshore oil and gas industry