The oil and gas industry in Libya has suffered a number of health and safety accidents including environmental disasters due to the nature of the work involved and the hazardous materials it handles in all facets of exploration and production. Such issues have hitherto not received due attention by the Libyan Authorities. The fact that strict HSE assessment standards are neither well-defined nor established in Libya is not helpful. Furthermore, oil and gas industry in new free Libya has suffered immensely during the 2011 Arab Spring and its rebuilding poses a number of critical HSE challenges. The purpose of the research is to develop and validate a HSE Performance Review Methodology for Libyan oil and gas industry based on clearly defined and measurable aspects for assessment. The thesis starts by performing a comprehensive literature review on all aspects of HSE including universal standards. The review indicates that there is a gap in respect of semi-qualitative methods for assessing HSE performance commensurate with other disciplines. The thesis then identifies four key research problems in the context of Libyan oil and gas industries. Based on these problems, an empirical research was conducted and included three distinct Stages. Stage 1 consisted of a pilot study based on an interview questionnaire with 15 experienced HSE professionals working in oil and gas companies in Libya to help identify key issues pertaining to HSE assessment. Data analysis results for Stage 2 have been used to derive a list of 12 main groups of HSE questions which have then been tested on 84 HSE professionals working in Libya stemming from 35 medium and large oil and gas companies. Modal distribution analyses have been performed to scope down the number of HSE performance factors, which would then be used in Stage 3 of the empirical research. This consisted of issuing the same 84 interviewees with a questionnaire requesting their assessment of how Critical, Important and Less Important were the 60 factors identified. Central Tendency, Variation Ratios and Indices of Diversity were used to successfully analyse the data. With the QAA Subject Review in mind as a potential model for the sought methodology, and a mapping of the four research problems with data analysis results from Stages 1, 2 and 3; six HSE Performance Review Aspects emerged: Prevention, Surveillance, Response, Achievements, Resource and HSE Management and Enhancement – judged and graded using a 1 to 4 scale. The HSE Performance Review methodology has been validated by direct application to five comprehensive studies starting from the self-assessment document written by the companies, an extensive review visit by peer-assessors and a final report showing grades, benchmarks and shortcomings. Lessons learned from the validation exercise have been used to revise the definition of the six Aspects and used to propose an appropriate implementation plan in Libya. The results of the validation exercise are very encouraging and readily confirm that the methodology can be applied to other industry sectors.