Fox's "House" celebrated its 100th episode with a ratings win Monday night, tying for first place with CBS' "Two and a Half Men."

"House" scored a 5.5 rating/13 share among adults 18-49 and 14.7 million viewers, according to preliminary Nielsen Media Research numbers. Although tied for first, the episode was down 8% from its rating last week, when it hit a season high. A new episode of "24" was down 14% from last week and marked its lowest Monday night rating season-to-date. Fox still finished the night first in the demographic with a 4.6/11 and second among viewers with 13 million.

CBS had new episodes across the board, with all comedies performing about average for the season. "CSI: Miami" scored on the high side, helping the network finish in second with a 4.3/10 and first in average viewers with 13.3 million.

ABC's "The Bachelor" reached season-to-date highs and logged the franchise's highest rating since its November 2007 finale. At 10 p.m. a new episode of "True Beauty" was about on par with its last original episode. ABC's average 3.7/9 (9.6 million) for the night gave the network third place.

After a Sunday promo blitz during the Super Bowl, "Chuck" and "Heroes" returned with new episodes, followed by the season premiere of "Medium." A special 3-D episode of "Chuck" gave the network its highest non-Olympic time period rating in 11 months, reaching season highs. "Heroes" came back on par with its season average from last fall and delivered its best rating since October. In the 10 p.m. slot the fifth-season opener of "Medium" was the series' lowest-rated premiere but saw the best rating in the time period since November. NBC finished fourth with a 3.3/8 (8.4 million), its best Monday night since the day before the presidential election, when NBC aired "Deal or No Deal" and "Saturday Night Live Presidential Bash '08."

On The CW, "Gossip Girl" improved 10% over its last original episode and "One Tree Hill" remained flat. The network averaged a 1.2/3 (2.4 million) for the night, and posted a 2.6 rating among women 18-34.

	8	8:30	9	9:30	10	10:30
3.7 / 9	The Bachelor 4.1 / 10 11 million				True Beauty 3.0 / 8 6.8 million
4.3 / 10	The Big Bang Theory 4.1 / 10 10.9 mil	How I Met Your Mother 4.2 / 10 10.2 mil	Two and a Half Men 5.5 / 12 16.5 mil	Worst Week 3.1 / 7 10 mil	CSI: Miami 4.4 / 11 16 mil
4.6 / 11	House 5.5 / 13 14. 7 mil		24 3.7 / 8 11.3 mil		No Programming
3.3 / 8	Chuck 3.0 / 7 8.3 mil		Heroes 3.9 / 9 8.5 mil		Medium 2.9 / 7 8.5 mil
1.2 / 3	Gossip Girl 1.1 / 3 2.3 mil		One Tree Hill 1.3 / 3 2.6 mil		No Programming

Source: Nielsen Media Research

*Ratings are specified in the 18- to 49-year-old demographic and viewership in P2+.

A note about ratings: Ratings are expressed as percentages of Nielsen's estimated 114.5 million U.S. television households. The first number, the rating, is a percentage of households tuned into a specific program at a specific time.

The second number, the share, is a percentage of households with televisions in use tuned into that same program. For example, if a show obtains a 10.2/16, this means that 10.2% of all U.S. households tuned into the program at some point during the broadcast. Meanwhile, 16% of all households watching television during the time period viewed the program at some point. Ratings are broken down further by demographic, as networks sell advertising time based on the makeup of the audience.