Afghanistan continues to struggle as a state due to the many contending ethnic, religious and regional rivalries. Regional commanders, the illegal drugs trade and the continuing Taleban insurgency hamper the rule of law, development and aid efforts.
Millions of people have left their homes to flee conflicts and natural disasters in recent years. Since 2002, the UN-backed voluntary repatriation programme has helped more than 3,725,000 people return from abroad, mainly from Pakistan and Iran.
Thousands have been internally displaced, especially in the south as a result of the insurgency - which has intensified since 2006.
In 2006, more than 3,000 Afghans died in the violence, twice as many as in 2005 and more than in any other year since the 2001 fall of the Taleban, says Human Rights Watch.
Years of conflict and population movement make any census difficult.
Recent estimates suggest Pashtuns comprise nearly half the population. Tajiks form the second largest group, followed by Uzbeks and Hazaras.
About 99% of Afghans are Muslim - more than three-quarters of them Sunni.