Accurate data on mortality levels and causes of death is critical to assist governments to improve the health of their populations; by identifying priority areas for intervention, leveraging resources for such interventions, and to monitor the impact and effectiveness of health programs. To date, there has been little data available to agencies on mortality and causes of death in the Pacific Islands, and there is significant disparity in published estimates, with many considered implausible. Further, there are indications that improvements in life expectancy (LE) across the region have stagnated in contrast to previously published estimates, most likely as a consequence of premature adult mortality from non-communicable diseases (NCDs).In this research, routine vital registration collections from Pacific Island countries are examined to determine whether these data can improve our understanding of mortality and causes of death in the region. The work presents a review of available data, examines the potential flaws and biases in the data collections, and examines the methods best suited to working with the identified collections to generate valid, reliable estimates of mortality level and cause of death, disaggregated by age group and sex. Due to the scale and diversity of the Pacific Islands, six countries representing a broad range of population size, level of development, and all three sub-regions were selected for review. These were: Nauru, Fiji, Kiribati, Palau, Tonga and Vanuatu.Reporting systems were evaluated to identify potential impacts on the quality and completeness of available data using an assessment framework that considers the ii societal, administrative and system (administrative, technical and ownership) influences on the reporting system. Substantially more data was found to be available than has been previously analysed or published. Medical certificates of death are completed for some deaths in all of the study countries, and are required for all deaths in Nauru, Fiji, Tonga and Palau.Analytical strategies for deriving estimates of mortality level by age and sex were selected from available approaches based on the system assessments, data available and level of migration. Methods employed included direct calculation of mortality level and evaluation of trends over time (Nauru and Palau), evaluation of published data to establish plausible trends (Fiji and Tonga), direct demographic methods to assess completeness -the Brass Growth Balance analysis (Fiji), and capture-recapture analyses (Tonga and Kiribati). Only Vanuatu had insufficient data from routine collection systems to reliably generate mortality estimates. Findings from the use of model life tables in comparison to mortality estimates from empirical data in the other study countries were therefore reviewed to evaluate the plausibility of published estimates of mortality level from Vanuatu.Estimates of cause-specific mortality were calculated directly from the medical certificate data for Palau where the system review in...