Whenever Ivan Lendl wins another tournament the inevitable question arises: Why isn't he ranked higher than fourth in the world?

After winning last night's D.C. National Bank Tennis Classic championship, Lendl's record for the last 10 months stands at 101 victories and five defeats. He has won nine tournaments this year and been runner-up three times. Moreover, he has beaten John McEnroe, still ranked No. 1 in the world, four straight times. No one in professional tennis can touch that.

Lendl, however, refuses to campaign for himself. Asked last night if he is the best player in tennis, Lendl bristled and firmly said, "No comment." Asked if he should be ranked higher, he said, "I don't like to talk about it."

Jimmy Arias, who lost to Lendl last night, said Lendl "is probably the best ground stroker in the game. He's got strong everything; a big serve and a huge forehand."

Arias was asked if he considers Lendl the best in the world. "I don't know," he replied. "You'd have to ask John McEnroe about that."

Feuding within the tennis world is partly responsible for Lendl's ranking. Five of his recent championships have come in World Championship Tennis events. But the Association of Tennis Professionals, which until recently had the only computer ranking service, only recognizes the Grand Prix tournament records. (Many of the WCT tournaments have only 16-player fields, the ACT reasons.)

A new computer ranking service--called Nixdorf--was started last month by the WCT, and it takes into account results in WCT, Grand Prix and Davis Cup matches.

Nixdorf's first ranking, released during Wimbledon, places Lendl No. 1. As Nixdorf gains the respect of the tennis world, the question of "Who's No. 1?" will become even more muddled, like the confusion the WBC versus the WBA offers in boxing.

And with many of the top-ranked players so choosy about the court surface they will play on, thereby limiting face-to-face competition among the very best, computer rankings provide almost the only means of comparison.

The other knock against Lendl, 22, is that he hasn't won a Grand Slam event: Wimbledon, U.S. Open, French Open or Australian Open.

His victories in the Volvo Grand Prix, the Swiss Indoor, Argentine and South American opens, Canadian Open and the Volvo Masters apparently aren't impressive enough.

"They always say you have to win one of the majors to be No. 1," John Harris, this tournament's codirector, said last night.

"Jimmy Connors won Wimbledon, so maybe he could be considered No. 1," Harris said. "But week in and week out, there is no player whose record can compare with Ivan's the last nine months. Even though he's won all that money (more than $1 million already this year) and gotten a lot of television exposure, a lot of his victories have come in WCT events. And that can't help his ranking."

After last night's championship, worth $32,000 to Lendl, he said he is playing better than he was before a four-week vacation in June and July. "But I can still play better," he added, which means trouble for others during the rest of the summer tour.

Asked if winning summer tournaments is more important, because he hasn't won a Grand Slam event, Lendl replied, "No, it's you guys (reporters) who are always talking about that."

And while seemingly half the people on the grounds were arguing the relative merits of Lendl versus McEnroe versus Connors (No 2.) versus Guillermo Vilas (No. 3), Lendl walked away from the debate.

"I've heard people say," said Harris, "that Ivan Lendl laughs all the way to the bank."

Raul Ramirez and Van Winitsky defeated Hans Gildemeister and Andres Gomez for the doubles championship, 7-5, 7-6.