Katie Monahan, the leader in the international rider championship point standings at the Washington International Horse Show at Capital Centre, is also in first place on the American Grand Prix Association leading rider chart. Her total winnings are listed at $45,433.

Melanie Smith is the reigning World Cup Champion and the defending champion for the final President's Cup Grand Prix at this show.

Last night these two rivals -- not just the leading female riders, but the leading riders -- teamed as members of the U.S. Equestrian Team to win the $5,000 Sun Maid International Open Jumpers rotating pair relay. This class is as far as the specifications are concerned and one of the most popular with the spectators.

The rules dictate that the two riders must complete a course of jumps twice around. They can alternate which rider takes each jump, but must rotate each time the other makes an error. Monahan and Smith negotiated the course without faults.

"We both wanted to win," said Smith, 33, of Litchfield, Conn., who rode Grand Siecle. "When they (team officials) asked us how we wanted to team up for this event, we said the girls on one team and the boys on the other."

Part of the women's strategy last night involved watching their male teammates, Norman Dello Joio, of South Salem, N.Y., and Donald Cheska, of Waukesha, Wis., perform. "We changed our plan after watching them," said Monahan, 28, of Upperville, Va. "It's an advantage to go late." The male pair, fifth to enter the arena, finished sixth.

"When we came into the ring and the crowd screamed, we looked at each other and said we got to go," added Monahan, who rode Grey Chief. "The most exciting thing is the crowd is so into it," said Smith. "The crowd was so loud the second time around if Katie had hit a rail I wouldn't have heard it. It's the one class that is such a kick. There is just so much strategy."

Monahan and Smith were the 11th pair to compete; their winning time over the course was 58.96 seconds. Two entries later, brothers Thomas and Markus Fuchs made a challege, but could only manage to place second, finishing with a time of 59.8.

In other events yesterday, 32-year-old Don Stewart Jr., Jacksonville, Fla., took the lead in the Regular Conformation Hunter Division with 17 points on Henry The Hawk, owned by Eagle Nest Farm. The 1980 champion, Weather Permitting, owned by Cismont Manor Farm and August A. Busch Jr. and ridden by Charlie Weaver, was close with 16 points.