The signature extreme sports event of the year, the 1999 X Games will gather more than 400 of the world's best athletes to compete June 25-July 3 in San Francisco, Calif.

Following is a description of each of the scheduled events in the fifth annual X Games.

X Games event descriptions:
Aggressive In-Line Skating
(separate men's and women's disciplines; co-ed triples)
Street -- Skaters negotiate obstacles, ramps, etc. during a timed routine.
Vert -- Skaters perform tricks in the halfpipe during a timed routine.
Vert Triples - Teams of three (men and/or women) compete together in the halfpipe.

Bicycle Stunt Riding
Dirt Jumping -- Bikers perform high-flying maneuvers after launching from a dirt ramp.
Street -- Bikers negotiate obstacles, ramps, etc. as part of a timed routine.
Vert -- Bikers perform tricks in the half pipe during a timed routine.
Flatland -- Bikers perform difficult and technical tricks as part of a timed routine on flat land.

Freestyle Moto-X (new for 1999)
Motocross riders perform maneuvers after launching from dirt ramps.

Skateboarding
Best Vert Trick (new for 1999) -- Online voters will judge the best trick performed on a skateboard.
Street -- Skateboarders negotiate obstacles, ramps, etc. during a timed routine.
Vert -- Skateboarders perform tricks in the halfpipe during a timed routine.
Vert Doubles -- Skateboarders perform halfpipe tricks in teams of two.

Skysurfing
Surfer and camera flyer jump together and combine efforts for an overall team score.
Snowboarding
separate men's and women's disciplines
Big Air -- Boarders are scored on the difficulty, execution and height/length of jumps on a man-made jump.

Sport Climbing
separate men's and women's disciplines for each event
Bouldering (new for 1999) - Ropes and harnesses are not used to negotiate a route (pads/mats are used); multiple attempts are allowed within the allotted time.
Speed -- Climbers ascend the wall at top speeds in a head-to-head race format.

Street Luge Racing
Dual -- Racers on sleds with wheels travel at 60 miles per hour in a head-to-head format.
Super Mass -- Racers compete in groups of six.

Wakeboarding
separate men's and women's disciplines
Boarders perform tricks in the water while being pulled by a motor-powered boat.