16th Century—Sao Tome colonised by the Portuguese, who bring in slaves to work sugar plantations. Becomes important staging post for slave trade.
1800s—Cocoa introduced. Sao Tome develops into one of world's main cocoa producers.
1951—Becomes overseas province of Portugal.
1960—Formation of nationalist group which later becomes the socialist Movement for the Liberation of Sao Tome and Principe (MLSTP).
1974—Military coup in Portugal. Portuguese government recognises islands' right to independence, acknowledges MLSTP as sole representative in negotiations. Unrest followed by exodus of Portuguese.
1978—Government announces suppression of coup attempt, brings in Angola troops for support.
1979—Trovoada arrested, accused of complicity in coup attempt. He is released and goes into exile in 1981.
1980s—Government scales down links with communist world as economy deteriorates. Declares itself nonaligned, seeks Western support for recovery plans.
1990—New constitution allows opposition parties, provides for multi-party elections and restricts president to two five-year terms. Trovoada returns from exile.
1991—First multiparty elections. Renamed MLSTP-PSD loses majority. Transitional government installed, pending presidential elections, subsequently won by independent candidate Trovoada.
1992—Popular unrest sparked by austerity measures.
1994—MLSTP-PSD regains power. National assembly grants Principe local autonomy.
1995—Trovoada toppled and detained in bloodless coup by soldiers but is reinstated within days after pressure from donor countries.
1996—Trovoada re-elected president. Popular protests over economic hardships.
1997—Unrest over economic conditions.
Sao Tome establishes formal diplomatic relations with Taiwan at Trovoada's behest. The move is condemned by the government. China retaliates by suspending ties.
1998—MLSTP-PSD wins general elections, Guilherme Posser da Costa appointed prime minister.
2000—Civil servants strike to press for higher pay. Officials say country's external debt in 1998 amounted to US $270 million, more than five times the country's annual gross domestic product of around US $50 million.