Welfare issues and approaches are compared in the following review, for all major meat chicken producing countries. In certain countries, such as the United States and Australia, the industry comprises a small number of integrated, self-regulated companies, whereas in Europe the industry is more diverse, with greater competition, and more government regulation. There is much more meat chicken welfare research and regulation in Europe, and in particular the United Kingdom, than in countries with self-regulated industries, such as the United States, even taking into account the level of meat chicken production in the relevant areas. By contrast, welfare regulation in two of the world's major meat chicken producing countries; namely Brazil and China, is negligible. Some welfare issues are regional, such as high temperatures which are particularly problematic for free range birds, breeds selected for rapid growth and when birds are removed from fully-housed systems. However, similar welfare issues affect intensively-housed birds worldwide, which comprise the majority of animals produced. These include rapid growth rates, predisposing birds to heart and leg problems, especially ascites and sudden death syndrome, and high stocking densities, which inhibit locomotion and environmental exploration, predisposing birds to contact dermatitis. Welfare research in Europe has shown that highly stocked birds spend longer sleeping, congregate around feeders and are more fearful, as well as experiencing higher ammonia levels, which irritate their eyes and respiratory systems. The review concludes that intensive systems present similar welfare issues worldwide; however, European research is more directed to the behavioural and cognitive requirements of the birds, than in self-regulated countries. This will enable their industry to respond better to future welfare requirements from consumers.