With Michael Phelps setting a record for the most Olympic gold medals ever won in a career, NBC posted its highest-rated night of the Games so far.

And ratings could climb higher yet, with three primetime races yet to go for the superlative U.S. swimmer.

NBC averaged a 19.9 household rating and 34 share Tuesday night for the 8 p.m. to 12:19 a.m. window, according to Nielsen. That bettered Sunday’s 17.9 rating, previously the best night of the Olympics, and was 9 percent ahead of an 18.3/30 for the same night in Athens four years ago.

The network averaged 34 million total viewers and an 11.3 adults 18-49 rating, NBC’s best numbers on any night since Feb. 19, 2002, during the Salt Lake City Olympics. Among total viewers, Beijing bested Athens by 11 percent, or 3.9 million viewers.

Some 82 million viewers tuned into some portion of NBC’s primetime coverage, and 168 million viewers have watched NBC Universal’s coverage through the first five days of the games, 15 million more than for Athens.

Over the first five days of the Games, NBC is averaging 31.3 million total viewers, up 21 percent from 25.8 million in Athens. NBC is on pace for its highest-rated non-U.S. Summer Games since Barcelona 1992, and the best could be yet to come.

Tuesday night’s coverage featured the U.S. women’s gymnastics team’s silver medal-winning performance as well as Phelps’ two historic wins, and both will be in action again tonight, with the individual all-around gymnastics competition and Phelps’ 200-meter individual relay.

Phelps will be going for his sixth gold medal of this Games and 12th overall. He’s won all five of his previous races in world record time, but NBC has been touting fellow American Ryan Lochte as a potential challenger to Phelps in tonight’s race.

The two teammates finished within 0.01 of each other in yesterday’s semifinals.
The gymnasts, too, should be a huge draw with Americans Shawn Johnson and Nastia Liukin both capable of capturing the all-around title.

And though Saturday nights usually draw lower ratings than other nights of the week, NBC is setting up for a potentially record-breaking night this Saturday as well. That’s when Phelps will swim his final race, when he could break Mark Spitz’s single Olympics record with his eighth victory. The network will reportedly air the race live in all time zones, after using taped coverage in the West thus far this Games.

NBC also released updated numbers for NBCOlympics.com yesterday. Through five days, the site has already surpassed Athens’ numbers, with 21.1 million unique users versus 11.1 million for the entire Athens Games, a jump of 90 percent.

Page views are up 63 percent, from 229.9 million to 373.9 million. And video streams have seen the biggest jump, up 705 percent, from 2.2 million to 17.7 million.