Professionals who treat everyone the same are likely to be insensitive to and unaware of the diverse needs of different people and their rights to equal opportunities. The conceptualization of diversity outlined in Chapter 1 supports the integration of diversity and equality. Sustainable development can then achieve fairness and equality along with the environmental and economic objectives. This chapter sketches out how different countries address diversity and equality and introduces the strategy of mainstreaming as a means of building in a consideration of diversity and equality to all aspects of planning. Part 1 starts by looking in broad terms at legislative frameworks in a range of countries. Part 2 looks at the current evidence for diversity and equality in spatial planning in the UK. Part 3 introduces mainstreaming as a strategy, showing how it developed, particularly in the European context; how it has been applied to environmental and equality issues and what lessons can be learnt by looking at mainstreaming through innovation theory.