Abstract : A Remotely Operated Vehicle (ROV) reliability study was initiated to determine how ROVs can be designed and built to achieve enhanced operational reliability when operated during extended underwater deployment. The contractor was to examine the technology used in the design and construction of representative ROVs which are currently state-of-the-art and document proposed design or construction methodology to effect high reliability. This study report is the result of the contractor's study efforts. The study result revealed that the process of development and procurement of ROVs for Navy use presently involves modification of off-the-shelf commercial vehicles. Long term reliability is not a design criteria for commercial vehicles and is certainly lost in the development process due to cost competition. As a result, commercial grade vehicles with broad applications are modified for specific requirements. These vehicles have reliability and other problems as described in detail in this report. Present state-of-the-art ROVs cannot be modified to meet the requirements for reliability of extended deployment vehicles. Development of a highly reliable long term deployment vehicle requires the rigorous use of a through development process. Simultaneously with any development, efforts should be initiated now to develop technological approaches and design and manufacturing criteria to address the long term reliability problems identified in this study.