Isopoliteia, i.e. the right of equal citizenship, has been applied individually or massly for political, economic and cultural reasons in the Hellen societies. It appears to be in the texts of the Treaty in different ways. In particular, epigraphic sources and ancient sources provide information. The city of Miletos also had a wide network of colonials, and from time to time it established agreements on the Isopoliteia rule for different reasons. These treaties appear to sometimes be repeated at certain periods. In order to re-establish the population they lost after the Persian demolition, he also made some treaties for political and economic reasons. We will also try to make an assessment of the concept of isopoliteia, one of the facts in the Hellen world, based on the epigraphic, ancient and modern sources on Miletos. We think this assessment will contribute to identifying its impacts and projections on the history of the former Western Anatolia.