44 Asian teams are affiliated with FIFA, but Cambodia, Philippines, Bhutan and Brunei decided not to take part, and Myanmar were banned from the competition (for refusing to play a qualifier in Iran during 2002 qualifying), so a total of 39 teams took part, competing for 4.5 places in the World Cup.

Only the 14 last ranked teams according to FIFA took part in the Preliminary Round, where they were paired 2-by-2 and played home-and-away knock-out matches.

The first leg was originally played on 3 September 2005 but the match was ordered to be replayed by FIFA after a refereeing mistake.

With Uzbekistan leading the tie 1–0, a penalty was awarded to them but the referee disallowed the resulting goal and offered an indirect freekick to Bahrain for encroachment.

The Fourth Round winner then played the fourth-placed team of the CONCACAF qualifying group, Trinidad and Tobago, in a home-and-away play-off.