A chronology of key events:
1500s - Ottomans absorb part of Yemen into their empire but are expelled in the 1600s.
1839 - Aden comes under British rule, and when the Suez Canal opens in 1869 serves as a major refuelling port.
1849 - Ottomans return to north, but later face revolt.
1911 - Treaty between Ottoman Turks and Imam Yahya grants special rights to interior Zaydi tribes of Shia Muslim sect.
1918 - Ottoman empire dissolves, North Yemen gains independence and is ruled by Imam Yahya.
1948 - Yahya assassinated, but his son Ahmad beats off opponents of feudal rule and succeeds his father.
1962 - Imam Ahmad dies, succeeded by his son but army officers seize power, set up the Yemen Arab Republic (YAR), sparking civil war between royalists supported by Saudi Arabia and republicans backed by Egypt.
South Yemen formed
1967 - Formation of southern Yemen, comprising Aden and former Protectorate of South Arabia. Country is later officially known as the People's Democratic Republic of Yemen (PDRY). Programme of nationalisation begins.
1971 - Thousands flee to north following crackdown on dissidents. Armed groups formed in bid to overthrow government.
1972 - Border clashes between YAR and PDRY, ceasefire brokered by Arab League. 1978
- Ali Abdallah Saleh named as president of YAR.
1979 - Fresh fighting between YAR and PDRY. Renewed efforts to unite the two states.
1982 - Earth quake kills 3,000.
1986 - Thousands die in south in political rivalry. President Ali Nasser Muhammad flees the country and is later sentenced to death for treason. New government formed.
North and south unite
1990 - Unified Republic of Yemen proclaimed, with Saleh as president.
1991 - Yemen opposes US-led action against Iraq in Gulf War. This results in the return of 800,000 yemenis from Gulf Arab states.
1992 - Food price riots in major towns.
1993 April - Coalition government formed, made up of ruling parties of former north and south.
1993 August - Vice-President Ali Salim al-Baid withdraws to Aden, alleging that south is being marginalised and that southerners are being attacked by northerners.
1994 - Armies of former north and south, which have failed to integrate, gather on former frontier as relations between southern and northern leaders deteriorate.
1994 May - Saleh declares state of emergency and dismisses al-Baid and other southern government members following political deadlock and sporadic fighting. Foreigners flee escalating fighting.
1994 May 21- Al-Baid declares independence of Democratic Republic of Yemen. Saleh rejects secession as illegal.
1994 July - Northern forces take control of Aden, secessionist leaders flee abroad and are sentenced to death in absentia.
1995 - Yemen, Eritrea clash over disputed island territory.
US vessel attack
2000 October - US naval vessel USS Cole damaged in suicide attack in Aden which is subsequently blamed on al-Qaeda. Seventeen US personnel killed.
2000 October - Bomb explodes at British embassy. Four Yemenis who are jailed say they carried out attack in solidarity with Palestinians.
2001 February - Violence in run-up to municipal polls and referendum, in which voters show support for constitutional reform extending presidential term and powers.
2001 November - President Saleh visits US, tells President Bush that Yemen is a partner in the fight against terrorism.
2004: Yemeni forces kill rebel cleric
2002 February - Yemen expels more than 100 foreign Islamic scholars, including British and French nationals, in crackdown on terror and suspected al-Qaeda members.
2002 October - Supertanker Limburg badly damaged in attack, blamed on al-Qaeda, off Yemeni coast.
2003 April - The 10 chief suspects in the bombing of the USS Cole escape from custody in Aden.
2004 March - Two militants, suspected of masterminding bombing of USS Cole, are re-arrested.
Clashes in the north
2004 June-August - Government troops battle supporters of dissident cleric Hussein al-Houthi in the north; estimates of the dead range from 80 to more than 600.
2004 August - Court sentences 15 men on terror charges, including bombing of Limburg tanker in 2002.
2004 September - Government says its forces have killed dissident cleric Hussein al-Houthi, the leader of a revolt in the north.
2005 March-April - More than 200 people are killed in a resurgence of fighting between government forces and supporters of the slain rebel cleric Hussein al-Houthi.
2005 May - President Saleh says the leader of the rebellion in the north has agreed to renounce the campaign in return for a pardon. Minor clashes continue.
2005 July - Police and witnesses say at least 36 people are killed across the country in clashes between police and demonstrators protesting about a cut in fuel subsidies.