- 1955: The beginning of a separatist rebellion in the mainly Christian and animist south against domination by the Arab-Muslim north.
- January 1, 1956: Sudan, Africa's biggest country, becomes independent from Britain, and also from its northern neighbour Egypt.
- 1972: Accords signed in Addis Ababa between Khartoum and the southern rebels bring an end to 17 years of war, giving the south autonomous status.
- 1983: President Gaafar al-Nimeiry's decision to end the autonomous status and enforce sharia, or Islamic law, sparks a new rebellion in the south after 11 years of peace. Dissident colonel John Garang founds the Sudan People's Liberation Army (SPLA).
- 1989: Omar al-Bashir takes power in an Islamist coup and cracks down again on the southern rebellion.
- 1995: The northern opposition unites with the southern guerrillas to battle the regime.
- January 9: The two sides sign a US-brokered ceasefire agreement, providing for a six-year period of autonomy for the south followed by a referendum. The war killed more than two million people.
- July 9: Bashir sworn in as president, Garang as vice-president.
- July 30: Garang killed in a helicopter crash. Replaced by Salva Kiir.
- September 20: National unity government announced after weeks of bitter wrangling.
- October 22: Kiir forms an autonomous government for south Sudan.
- December 27: South Sudanese former rebels rejoin the national government, two months after walking out because of disputes over the implementation of the peace deal.
- May: Fighting breaks out in the flashpoint oil-rich Abyei region, threatening the peace process. Dozens are killed and more than 50,000 displaced.
- July 22: The Permanent Court of Arbitration in The Hague reduces Abyei's borders, leaving its main oil fields in the north. The referendum is planned in the south for January 2011.
- December 29: Adoption of the referendum law. Tribal violence which has killed 2,500 over the year leads to fears of a civil war in the region.
- April 11-15: Kiir becomes the south's first elected president following the first multi-party elections in Sudan since 1986.
- July 11: Khartoum and Juba start negotiations on key post-referendum issues, namely security, citizenship, the economy and respect for international treaties.
- September 24: The Khartoum government says it will accept the result of the vote after world leaders, meeting at the United Nations, call for the southern referendum to go ahead peacefully and on time.
- October: Kiir offers an amnesty to rebel fighters and seeks to reconcile with his leading political adversary, former foreign minister Lam Akol. Since January around 900 people have been killed in violence in the south, according to the United Nations.
- November 15-December 8: Voters register for the referendum.
- December 13: The United States says there is a recognition that a referendum in Abyei will not take place on January 9 as planned, but urges the parties to continue working for a solution to the disputed border region.