“America’s Got Talent” had the summer’s biggest debut last week. The question was whether it would grow into the summer’s biggest hit or shrink into simply a solid show in week two. The answer: It shrank.

A 60-minute “Talent” averaged a 3.8 adults 18-49 overnight rating last night, down 17 percent from last week’s 4.6 for its two-hour debut. It tied with Fox’s “So You Think You Can Dance” in the 9 p.m. hour, one week after besting it by 0.4 rating points.

“Dance” was also down slightly week to week, from a 4.0 to a 3.8.

In week one, “Talent” grew from start to finish, indicating that it could have an even stronger week two if all those who tuned in by the end came back. While “Talent” did jump 17 percent, from a 3.6 to a 4.1, from its first half to its second, that was well off the 4.8 it earned at its peak last week.

Perhaps viewers were bored by the show’s striking similarities to “American Idol,” the singing show on which Simon Cowell is a judge. He’s the producer of “Talent,” and the show’s format, right down to the one British judge, one female judge and one “why’s he here?” judge, mimics “Idol.”

Perhaps, too, some who sampled “Talent” last week returned to “Dance” or went off to cable, where the NBA Draft was on ESPN.

Meanwhile, Fox led for the night among adults 18-49 with a 3.4 rating and 11 share, followed by NBC at 2.8/9, CBS at 2.0/6 and Univision at 1.7/5. Trailing were ABC at 1.1/4, the WB at 0.8/2 and UPN at 0.4/1.

At 8 p.m., Fox was No. 1 with a 3.0 rating for "Dance," followed by NBC's 2.1 for a "Talent" rerun and Univision's 1.9 for "La Fea Mas Bella." CBS and ABC shared the No. 4 spot at 1.4 each for the special "Shark: Mind of a Demon" and reruns of "George" and "Freddie," ahead of WB's original and repeat "Blue Collar TV" at 0.9 and UPN's repeats of "One on One" and "All of Us" at 0.5.

At 9 p.m., Fox and NBC shared the lead at 3.8 each for "Dance" and "Talent." CBS was No. 3 at 2.0 for a "Criminal Minds" repeat, ahead of Univision's 1.6 for "Barrera de Amor," ABC's 1.0 for a "Lost" repeat, WB's 0.6 for a "One Tree Hill" rerun and UPN's 0.4 for repeats of "Eve" and "Cuts."

At 10 p.m., NBC was No. 1 with 2.6 for a "Law & Order" repeat, leading CBS's 2.5 for a "CSI: NY" rerun, Univision 1.6 for "Don Francisco Presenta" and ABC's 1.0 for another "Lost" rerun.

Among households, NBC was No. 1 with a 6.0 rating and 11 share, ahead of Fox at 5.7/10, CBS at 4.8/9, ABC at 2.4/4, Univision at 2.0/4, WB at 1.3/2 and UPN at 0.9/2.