If you're talking about 91 4x400-meter relay races in which a total of 5,140 high-schoolers - 2,576 boys and 2,564 girls - run one lap over a period of nearly 71/2 hours . . .

If you're talking about a quartet of men ages 75 and over motoring down the track for 100 meters while a crowd of nearly 50,000 urges them on . . .

If you're talking about Olympic gold medalists running in front of the largest crowd they will ever see in the United States (except in rare Olympic years) . . .

If you're talking about the old-timers at the northeast corner of the stadium going "wooooo" when two runners are battling for the lead entering the final turn with 100 meters to go . . .

Then you're talking about the Penn Relays.

The 113th edition of what we like to call the world's oldest, largest and best track and field carnival gets under way in earnest today. A total of 315 events - plus multiple heats in some - spanning 35 hours over three days will be conducted before the last runner crosses the finish line about 6 p.m. Saturday.

Here are a few things to know before you head down to Franklin Field:

Hail the champions. Twelve athletes who won individual titles in the NCAA indoor championships last month, along with two championship relay teams, are competing at the carnival. One runner, Kerron Stewart of Auburn, won the women's 60 meters and 200. Another, Florida State sprinter Walter Dix, joins four other athletes who captured individual titles at last year's NCAA outdoors.

Arrive early. Because of an earlier time for the national telecast on Saturday (1-3 p.m., ESPN2), the carnival will conduct five of the six USA vs. the World relays between those times. The sixth, the women's sprint medley relay, will be run at 11:55 a.m.

Win-seeking I. Florida State, the defending NCAA and Atlantic Coast Conference outdoor champion, is looking for its first win ever in men's competition at the relays. The Seminoles have a good shot in the 4x100, 4x200 and sprint medley.

Win-seeking II. Wisconsin, which is entered in Saturday's 4x1-mile relay, is searching for its first victory in a men's relay at the carnival since the Woodrow Wilson administration - 1916, to be exact.

They're already winners. A determined women's team from Virginia Tech, which won the ACC outdoor championship last weekend while still reeling from the unspeakable tragedy on its campus, competes today in two relays and the 400-meter hurdles.

Football, anyone? Jamaal Charles, a starting running back from Texas, and Michael Ray Garvin, a backup defensive back for Florida State, will compete in the sprint relays.

Lone ranger. Senior Mike Morrison, a graduate of Willingboro High, will be the only representative of the Florida Gators, men or women, at the relays. He will compete Saturday in the long jump, an event he won here in 2005.

Cheerio, England! A team from the University of Birmingham is scheduled to compete in a pair of men's championships - tomorrow's distance medley and Saturday's 4x1 mile. No team from England has won at the carnival since Oxford in 1956.

Run, repeat. Nicodemus Naimadu of Abilene Christian will try to become only the second runner in history to win three consecutive 3,000-meter steeplechase events at the carnival during tonight's distance running program.

Changing sides. Anna Willard, a graduate student at Michigan who is scheduled to run on the Wolverines' 4x1,500 team tomorrow, led Brown to a third-place finish in the distance medley last year. She holds 10 school records at Brown.

Dueling jumpers. One of the more entertaining competitions Saturday could come in the men's high jump, in which NCAA indoor champion Donald Thomas of Auburn renews his rivalry with Andra Manson of Texas, the 2006 winner at Penn.

The little guys. Lincoln and St. Augustine, the 2007 NCAA Division III and Division II indoor national champions, respectively, are bringing full squads of runners, and you can believe they will compete against their larger rivals.

How about 'Nova? Villanova, the winner of 88 men's and 26 women's Championship of America races over the years, will enter four relay events - the men's distance medley and men's 4x800, and the women's distance medley and 4x1,500. The women's DMR team won last year.

Don't forget . . . The Penn Relays program, topping out this year at 148 pages, is one of the world's best bargains at $8. It contains lineups, records, past results and anything else that will make your carnival experience more enjoyable.

Keep the car home. Unless you have a really good sound system in your vehicle, it is advised to take public transportation to the Penn Relays. Parking around Franklin Field is extremely limited, and traffic should be more tied up because of a ban on school buses on the South Street bridge. SEPTA's R1, R2 and R3 trains all stop at the University City station, less than 100 yards from the entrance to the stadium.

Tickets, please. Tickets for today and tomorrow are $14, $20 for reserved seats. General admission for Saturday is $20, while reserved seats for that day run from $30 to $45.