<Tr> <Td_colspan="2"> Next → Season 2 </Td> </Tr> <Tr> <Td_colspan="2"> List of 90210 episodes </Td> </Tr> <P> The first season of 90210, an American television series, began on September 2, 2008 . Gabe Sachs and Jeff Judah are executive producers for the first season, after original producer Rob Thomas dropped out to focus on other projects . The series premiered to 4.65 million viewers, and broke records for The CW at the time, becoming their highest rated premiere in viewers and in Adults 18--49 with a 2.6 rating . On September 22, 2008, after airing just four episodes, the network gave the series a full - season order of 24 episodes . </P> <P> Season one regular cast members include Rob Estes, Shenae Grimes, Tristan Wilds, Jessica Stroup, Dustin Milligan, Ryan Eggold, AnnaLynne McCord, Michael Steger, Lori Loughlin, and Jessica Walter . Along with special guests from the original series, Jennie Garth, Shannen Doherty, and Tori Spelling . Walter was replaced by Jessica Lowndes as a series regular in the thirteenth episode due to "financial reasons". The CW also hired Rebecca Sinclair to re-tool the series as head writer . She took over completely as executive producer by the end of the season, after Sachs and Judah resigned . </P>

How many episodes are in 90210 season 1