Update: Here's ABC's official take.
"Lost" (9:00-10:00 p.m.)
Opposite stiff original competition at 9:00 p.m. on CBS ("NCIS: LA") and NBC (second hour of a 2-hour "Biggest Loser"), ABC's "Lost" shot up over its lead-in by 5.3 million viewers (9.5 million vs. 4.2 million) and by 180% in young adults (4.2/11 vs. 1.5/4) and grew its audience throughout its broadcast. Despite CBS' (original "NCIS") and NBC's (first hour of "Biggest Loser") decided lead-in advantages coming into the time period, ABC's "Lost" finished a dominant No. 1 in the 9 o'clock hour with Adults 18-49 (4.2/11), outdelivering second-place "NCIS: LA" by 20% (3.5/9), third-place "Biggest Loser" by 24% (3.4/9) and fourth-place Fox's "Idol"-led "Glee" replay by 40% (3.0/8).
* "Lost" stood as Tuesday's No. 1 scripted TV show for the 6th straight week in Adults 18-49, Adults 18-34 and among key Men (M18-34/M18-49).
* "Lost" grew week to week in both Total Viewers (9.5 million vs. 9.3 million) and Adults 18-49 (4.2/11 vs. 4.1/10).
Source: ABC
Source: TVByTheNumbers