This paper reviews the existing body of scientific literature relevant to organic poultry production, in order to assess, and where possible quantify, the key issues affecting welfare. The review consists of three parts, covering health-related welfare issues in organic poultry production systems (breed suitability; nutrition; feed contribution from the range, range use and group size), health-related welfare issues for organic laying hens (feather pecking; endo-parasites and ecto-parasites), and health-related welfare issues for organic broilers (foot, hock and breast health). The evidence suggests that most health-related welfare issues are not specific to organic farms, but maintaining good health and welfare on organic farms can be challenging. There are many organic farms that do not have major problems, suggesting that husbandry (knowledge and technical skills) is crucial in managing welfare issues. There is also considerable variation in farming systems within the organic sector (ranging in farm size, housing and range quality, capacity to produce home grown feed, opportunities for pasture rotation etc.) which can be a constraint to solving welfare problems, particularly where managerial input has to be spread across a diversity of enterprises. It is recommended that efforts should be made to make existing knowledge more accessible to those involved in organic livestock production. This should include mechanisms for regular updating, and take account of the fact that data from published research may lag behind the levels of performance being achieved by the most able producers. Topics for further research were identified including subjects that have had little previous research, such as the catching and disposal of spent organic laying hens, management of parent flocks and keel bone breakages.