For a long time, the benefits of the human genome revolution have been restricted to people of the prosperous countries of the world. This special issue of "Community Genetics", however, aims to highlight the rapidly emerging impact of genetic diseases on the health of people in developing countries, where marriage often occurs within the same clan, tribe or ethnic group and where consanguineous unions are frequently preferred. As a result, communities living side by side may show very different disease profiles, and specific disorders can be found only in particular ethnic groups or castes. This publication presents the outcomes of community genetics programs in developing countries and migrant communities in articles specially commissioned from an international panel of experts. It is unique in integrating information on a wide spectrum of genetic diseases of populations living in the Near East and South-West Asia. The findings will also help to identify health needs.