The thesis principally examines the three categories of petroleum arrangements in Nigeria and gives examples of other developing countries. This study presents a systematic and in-depth analysis of both the structure and substance of some modern petroleum arrangements that have emerged in recent years and examines, the financial benefits of such associations. The thesis is divided into two parts. Part 1 deals with participation agreements, joint venture and production sharing contracts, whilst Part 2 examines mutual benefit and marginalisation of the host communities. These agreements are usually long-term, without any mechanism for renegotiations and are shrouded in secrecy and confidential clauses. A good example is the NNPC and Ashland oil contract. Due to this lacuna, it is usually the practice for renegotiation to be done through the passing of a legal notice or new law, resulting in the presence of quite a few laws in the petroleum industry and the attendant mystification. This practice would have been simple if renegotiation clauses were enshrined in the agreement, enabling changing circumstances; and confidential clauses removed, aiding transparency in the transaction. The study finds that some of the laws and the regulations are very old and clearly out of style with the times, not to mention in an industry that is forever changing and dynamic and further affected and determined by international factors. Further, the study also found that the activities of the oil and gas companies, to a great extent have not employed international best practices or remained compliant with the existing laws of the nation; resulting in oil spillages, various forms of pollution, serious health hazards, gross environmental degradations, rural agricultural destruction, distortion of social harmony and peace that exist in, and between host communities and have fuelled underdevelopment in these communities. As long as these social inequalities and injustice continue, human rights violations, gross mismanagement of natural resources, corruption in all forms and sizes exist and the activities of the participants in that sector are not addressed satisfactorily, so shall poverty, insecurity and serious threat to national existence and survival continue.