The population of Tanzania in 2003 was estimated by the United Nations at 36,977,000, which placed it as number 32 in population among the 193 nations of the world. In that year approximately 3% of the population was over 65 years of age, with another 45% of the population under 15 years of age. There were 98 males for every 100 females in the country in 2003. According to the UN, the annual population growth rate for 2000–2005 is 1.4%, with the projected population for the year 2015 at 57,800,000. The population density in 2002 was 39 per sq km (102 per sq mi). The most densely populated regions are the well-watered or elevated areas, particularly in the Usambara Mountains, around Kilimanjaro and Meru, on the shores of Lake Victoria, in the Southern Highlands, and in the coastal areas around Tanga and Dar es Salaam.
It was estimated by the Population Reference Bureau that 33% of the population lived in urban areas in 2001. The capital city and largest urban area, Dar es Salaam, had a 2002 population of 264,000. Other large cities include Dodoma, Zanzibar, Mwanza, and Tanga. According to the United Nations, the urban population growth rate for 2000–2005 was 5.4%.
The prevalence of AIDS/HIV has had a significant impact on the population of Tanzania. The United Nations estimated that7.8% of adults between the ages of 15–49 were living with HIV/AIDS in 2001. The AIDS epidemic causes higher death and infant mortality rates, and lowers life expectancy.