The debut of The CW's "The Vampire Diaries" bared its fangs last night, and scored the network's largest audience ever (4.84mil) for a series premiere, topping last year's 90210, according to preliminary live plus same day Nielsen ratings for Thursday, Sept. 10, 2009.

Taking over the lead-off position on Thursday night, "The Vampire Diaries" delivered The CW's highest ratings ever in the 8-9pm time period with women 18-34 (3.0/10), women 18-49 (2.8/8), teens (2.7/11) and female teens (3.4/14). It also scored the best performance here in adults 18-34 (2.2/8), adults 18-49 (2.1/6) and viewers (4.84mil) since Oct. 2007.
 
"The Vampire Diaries" out-performed last season's Smallville premiere by 114% in women 18-34, 75% in women 18-49, 22% in adults 18-34, 17% in adults 18-49 and 11% in viewers.

"The Vampire Diaries" built in the second half hour, growing 18% with women 18-34, 10% in adults 18-34, 17% in females 12-34, 14% in persons 12-34, 12% in women 18-49, 10% in adults 18-49 and 9% in viewers.

Competitively, "The Vampire Diaries" was second in the 8:00-9:00p.m. hour with women 18-34 and adults 18-34, behind only football. "The Vampire Diaries" also beat ABC and Fox in adults 18-49 and total viewers.

For its 5th season premiere, "Supernatural" improved over its strong premiere last year by 6% in women 18-34 (1.7/5). "Supernatural" also scored its best women 18-34 (1.7/5) and women 18-49 (1.7/5) ratings since Jan. 2009.

The CW's new combination of "The Vampire Diaries" and "Supernatural" scored the network's best Thursday ever with women 18-34 (2.4/7) and women 18-49 (2.2/6). This marks The CW's best Thursday since March 2007 with adults 18-34 (1.8/6) and the network's largest Thursday audience (4.1mil) since Sept. 2008.

Competitively, The CW was second on Thursday night with women 18-34 and adults 18-34. The CW did also beat ABC and Fox in adults 18-49 and viewers for the night.

Versus premiere Thursday last year, The CW is up 60% with women 18-34, 29% with women 18-49 and 6% with adults 18-34.