Background: Roma people, the largest minority in Europe live in segregated communites in several countries. The size of the Roma population is based on estimations deriving from various sources, whereas only narrative accounts of their living conditions have been available.
Methods: A comprehensive environmental survey of all settlements in Hungary (n = 3145) was carried out employing Roma field workers in order to locate and characterize segregated parts (colonies) of human habitats. Based on the collected data on environmental conditions and aggregate population numbers of the colonies, ranking of colonies and maps on their characteristics were prepared for all counties of Hungary.
Results: Seven hundred fifty-eight colonies were identified with approximately 134,000 inhabitants. Ninety-four percent of all colonies are populated dominantly by Roma. Most frequent environmental problems in the colonies were found to be lack of sewage and gas mains, garbage deposits, waterlogged soil and lack of water mains.
Conclusion: Census data cannot be used for policy design aiming at those Roma who are in greatest need of help; that is, living in segregated settlements (colonies). Colonies constitute disadvantaged living conditions of varying severity which can be quantified by a composite score based on indicators of access to services and presence of environmental dangers. The proportion of colony-dwelling Roma is approximately one-fifth to one-quarter of the estimated number of Roma people in Hungary.