The reliability of ocean systems is dependent on organizational factors. It has been shown that low probability / high consequence system failures are overwhelmingly induced by organizational factors. However, no methodology is yet widely accepted for the evaluation of this phenomenon or its accurate quantification. A qualitative complementary approach is proposed based on the CANL (Complex Adaptive Non-Linear) model. In the first part, the understanding of organizational processes that affect reliability is sought. The approach is applied to several case studies based on published information: the "Story of a Platform Audit" (where no failure occurred) and some offshore accidents. A methodology is proposed to complement regular safety audit procedures. The approach is shown useful also to improve post-mortem investigations. In the second part, quantitative probabilistic formulations are revised, based on the understanding obtained through the previous approach. Some of the limitations of these quantitative methods are pointed out. The Reliability State of an Organization is defined and a ranking for its evaluation is proposed. Preliminary guidelines are presented for the use of this approach as a framework to identify suitable quantitative methods for a given case. The use of a qualitative approach is demonstrated. A different insight into organizational factors is achieved based on a disciplined approach that relies on experience. Significant conclusions regarding quantitative methods, their limitations and appropriate use, are obtained. / Graduation date: 1999