Mongolia has about 3 times the land area of France, but less than 1% of France's population, 1 inhabitant per sq. km, and the lowest population density in the world. About half of the population is nomadic or semi-nomadic and lives in rural areas. This far-flung population over difficult terrain makes it difficult to find populations and provide children with the vaccinations they require. This inherent difficulty of carrying vaccines to the country's scattered mobile populations has been made even difficult in the current economic crisis being experienced as the country rids itself of a central planning system. Mongolia has an inadequate supply of logistic equipment, such as cars. Given Mongolia's sparse population and difficult terrain, the country's greatest need with regard to immunization is combination vaccines. Mongolia also needs to expand its laboratory capacity to provide the microbiological confirmation of atypical cases of infection and to conduct microbiological surveillance of wild poliovirus and serologic surveillance of the population's immune status. However, despite these many formidable obstacles, Mongolia has achieved 80-90% overall coverage with the vaccines of the Expanded Program on Immunization (EPI), and only 4 cases of poliomyelitis, 4 cases of pertussis, and 2 cases of tetanus have been reported since 1987. Furthermore, the number of diphtheria cases dropped to zero in 1992, and hepatitis B vaccine has been provided together with the 6 EPI vaccines since 1991.