The series was again hosted by Andrew G and James Mathison, with Ian "Dicko" Dickson returning to the show as one of the judges, along with Mark Holden, Marcia Hines and Kyle Sandilands.
[1] The show was in the top ten most viewed shows for the early part of the series and eventually dropped to around number eighteen and nineteen for quite some time due to hot competition from Channel 7's Kath & Kim.
The Top 5 performance show marked the re-commencement of higher ratings for the program and it reached number nine.
As in previous years, the theatre week, held at Sydney's Seymour Centre, consisted of three gruelling elimination rounds.
Based on these performances, each contestant was told, one at a time, whether they would become a part of the Top 24, or if their journey would end.
The semi-finals were run to the same format as the fourth season, with four groups of six performing solo in a live studio on Sunday, Monday, Tuesday and Wednesday night.
On the Thursday night, the first eight finalists through to the Top 12 were announced, along with another eight of the remaining 24 chosen for the Wildcard show.
Carl Riseley vocally supported axed judge Mark Holden on his departure in March 2008.
On leaving, Marty Simpson stated that he had been approached by Sony BMG in relation to a recording contract.
She was known for her powerful vocals, which were described by the judges at audition and throughout the series as "sending shivers down the spine" when she sang.
She sang at the Sydney New Year's Eve concert, performed an original song at a Sydney Martial Arts contest in January 2008 and in March 2008 she went on tour with South African band Malaika and toured in Macao (China) in September 2008.
Ben McKenzie (born 24 July 1990) is from Gosford, on the Central Coast of New South Wales.
Ben was falsely named by Today Tonight as being involved in "vote-rigging" and was the first of 4 in a row who were eliminated.
Ben has composed many original songs which he has been performing at small shows around Sydney & the Central Coast of NSW.
The film is a unique combination of horror and supernatural thriller, drawing influences from The Ring and Silent Hill and was released on YouTube January 2012.
Jacob Butler first auditioned for Australian Idol in 2005, but failed to make it past the Top 100 Group Performances.
Jacob reached sixth place in the Australian version of The X Factor television series in the same year.
Jacob tried out for Idol again at the 2007 auditions, singing "Don't Look Back In Anger" by Oasis.
Australia made him their second top 12 finalist after his rendition of Snow Patrol's "Chasing Cars".
At the end of 2007, Jacob performed at the Sydney New Year's Eve Concert alongside fellow Idol contestants Ben McKenzie and Tarisai Vushe.
Since Idol, Jacob has released his debut album "Reason" in Germany and other countries across Europe.
Since leaving Idol, Mark da Costa has gone back to performing regularly, and has been on tour with his band for most of 2008.
She is adopted and her birth mother was a Vietnamese opera singer who travelled around China singing with her grandparents.
On 19 October 2007, there was a special Australian Idol telecast, "Doing It For The Kids", to raise money for Ronald McDonald House and Telstra Child Flight.