Assad took the oath before assembled parliamentarians, vowing to continue serving the main principles of the Syrian Arab Republic - equality, freedom and socialism.
He was first elected president in 2000 after the death of his father Hafez al-Assad, who headed the country since 1971.
A total of 97% of voters supported Assad, nominated by the ruling Baath (Socialist Arab Rebirth) party, in the May referendum.
Despite his relative youth, Assad (born in 1965) is considered a balanced, pragmatic politician who has managed to deal with complicated situations despite constant external pressure on Syria.
In particular, Assad made a hard decision to withdraw Syrian troops and security services from neighboring Lebanon in the spring of 2005, after former Lebanese Prime Minister Rafik Hariri was assassinated by what many assumed was the Syrian intelligence service.
Gradually, the Syrian leadership was able to break an unspoken European blockade, which practically froze their relations with Damascus after Hariri's death.
Assad said Syria would resume peace talks with Israel only if there were preliminary guarantees that the Golan Heights, captured by Israel in 1967, would be returned to Syria.
"Our demands are unchangeable - the peace process should be based on the land for peace principle, which envisions full return by Israel of Syria's Golan Heights and withdrawal to the 1967 borders," Assad said during the inauguration ceremony.
Peace talks between Israel and Syria were suspended seven years ago because Israel refused to return the heights.
Assad has repeatedly offered to resume talks with Tel Aviv, but the Israelis have responded by demanding that Syria stop supporting Lebanon's Hezbollah movement and radical Palestinian groups, and abandon its strategic partnership with Iran.
