Nomadic living is one of the major lifestyles in Iran, due to the country's arid and semi-arid climates. Nomadism has played an important role in the Iranian economy, and is practised by thousands of tribal households. At present, however, although its economic role as a main supplier of dairy and protein products is quite influential, its social and political position has weakened due to the penetration of the modernisation process in all aspects of the Iranian society. A century ago, the nomadic population was prominent in the demographic structure of the country, possibly constituting about 25 per cent of the total population, but this had decreased to 1.7 per cent by 2008. This paper will investigate the transition of the tribal population, by reviewing the available statistics and then analysing these data in a historic context.