The Democratic Opposition of Serbia (Serbian Cyrillic: Демократска oпозиција Cрбије, romanized: Demokratska opozicija Srbije, abbr.

[2][3] Its presidential candidate, Vojislav Koštunica, defeated Milošević in the 2000 general election, while the DOS secured a majority of seats in the National Assembly.

[2][4] Koštunica's Democratic Party of Serbia left the coalition government in July 2001, in protest of the governments decision to extradite Slobodan Milošević to the ICTY, and officially left the coalition in July next year.

Social Democracy was pushed into the opposition in May 2001 after a split in the party, as the faction which was eventually recognized by the Supreme Court of Serbia as the legitimate name bearer, was not regarded as such by the DOS, which transferred all the positions held by the party members to the other faction's adherents.

In March 2003, after a split in this party, the Social Democratic Union was renewed, still being a member of the DOS, while the Social Democratic Party was excluded from the coalition in November 2003, after having announced that it would support the opposition's demand for government's depose.