After establishing a nice foundation behind “American Idol” last season, Fox drama “House” continues to add viewers this spring.

Last week, as Fox racked up its seventh consecutive victory among young adults, the second-year medical mystery established series highs (9.3 rating/23 share in adults 18-49, 22.71 million viewers overall), according to Nielsen Media Research.

It was the week’s No. 1 scripted program in 18-49 — the first time in more than six years a Fox skein could make that claim (since “Ally McBeal” in November 1999).

When the season wraps in six weeks, “House” is projected to finish up about 20% year-to-year, and it should rank as the No. 5 drama on TV in adults 18-49 — lagging only “Desperate Housewives,” “Grey’s Anatomy,” “CSI” and “Lost.” Last season, it finished eighth among dramas.

“American Idol,” of course, remained the week’s hottest program overall, with Tuesday’s performance episode (11.6/32 in 18-49, 28.83m) and Wednesday’s results show (10.8/26, 26.23m) taking the top two spots.

For the April 3-9 frame, Fox’s 4.2 rating/12 share in adults 18-49 — up a hefty 20% vs. the same week last year (3.5/10) — was well ahead of CBS (3.6/10), with ABC and NBC further back in a tie for third (3.1/9).

Fox also dominated among the 12-34 crowd (3.7/12), while CBS edged out Fox in 25-54 (4.6/12 to 4.4/11) and rolled in total viewers (12.4 million).

Also for Fox last week, “Unanimous” (6.2/15, 14.01m) remained a solid second to “Lost” on Wednesday. New comedies “The Loop” on Thursday (1.7/5, 3.61m) and “Free Ride” on Sunday (2.4/6, 4.74m) are struggling, though.

Sports was a factor in CBS’ success, with Monday’s NCAA men’s basketball final (6.2/16 in 18-49, 17.54m) performing well, although down relative to past years, and Sunday’s Masters golf overrun getting the net off to a very good start on that night (4.6/17 in 18-49 from 7 to 7:30).

Eye remained on top Thursday, although “CSI” may be losing some of its edge (7.4/19, 23.30m), while it was a good week for second-year Friday drama “Numbers” (3.8/11 in 18-49, 13.69m), which posted some of its best scores to date.

Also, “The Amazing Race 9” (3.1/9 in 18-49, 8.15m) provided a nice ratings upgrade in its new Wednesday 8 p.m. slot despite opposing reality entries “Deal or No Deal” and “Top Model.”

NBC saw another record score for Monday’s “Deal or No Deal” (5.9/15, 17.75m), which aired a special two-hour edition, and its “My Name Is Earl” was the week’s No. 1 comedy in demos (4.7/12 in 18-49, 10.21m).

Not so hot was new Wednesday drama “Heist” (1.8/4, 6.20m), which shriveled opposite tougher competish in its new 9 o’clock time period.

ABC was paced by Wednesday’s “Lost” (6.9/17, 16.38m from 9 to 10:05) and Sunday’s repeat “Grey’s Anatomy” (5.9/15, 13.57m) and two-hour “Extreme Makeover: Home Edition” (5.5/14, 13.20m).

Tuesday comedy “Sons & Daughters” (1.2/3 in 18-49, 3.21m) fell off the map in its fifth week, and fifth-place lead-in “Hope & Faith” (1.3/3, 4.19m) isn’t much better.

UPN edged out the WB in 18-34 (1.4/4 to 1.3/4), although both trailed Spanish-lingo broadcaster Univision (1.6/5). Frog saw weak results for its midseason skeins, including Tuesday’s bow of “Pepper Dennis” (1.0/3 in 18-49, 2.61m).

Among ad-supported cable nets, USA rode “WWE Raw” wrestling to a narrow victory over TNT in 18-49 (0.76 to 0.73), although things swung in the Turner net’s favor in 25-54 (0.91 to 0.83) and total viewers (2.43 million to 2.21 million).

TNT’s original movie “Avenger” starring Sam Elliott attracted 3.5 million viewers with its premiere Sunday, but a slim 0.8/2 in 18-49 and 1.2/3 in 25-54.

Spike’s third-season premiere of “The Ultimate Fighter” scored well Sunday (1.4/4 in 18-49, 2.43m). It set a network record in men 18-34 (2.9/10), where it ranked No. 1 among all TV programs in the 10 o’clock hour.

At FX, drama “Thief” settled for 1.34 million viewers Tuesday, down from the previous week’s premiere average of 2.54 million.

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On Monday of the current week, ABC scored with the opening installment of two-part original movie “The Ten Commandments” (4.6/11 in 18-49, 13.86m).

It didn’t garner the best of reviews, but the Robert Halmi production starring Dougray Scott as Moses produced ABC’s second strongest Monday 18-49 score since football ended and its largest overall non-sports aud in the slot since January 2004. Pic wrapped last night.

Also of note on the night was a lower score for CBS laffer “The New Adventues of Old Christine” (3.7/9, 11.42m), whose 82% 18-49 retention of “Two and a Half Men” (4.5/11, 14.05m) puts it in line with “Out of Practice” and “Courting Alex” in the slot earlier this season.

NBC won the night’s opening hour with “Deal or No Deal” (4.3/13, 14.47m from 8 to 9:02) and Fox moved to the top in demos at 9 with “24” (5.1/12, 12.49m). CBS drama “CSI: Miami” ruled as usual at 10 (5.3/14, 17.16m) although “Commandments” seemed to somewhat sap its strength.