When Paul Silas came into the National Basketball Association in 1964, taking stimulants was part of the game. But because of the nature and pace of professional basketball today - the demanding travel scheduled and refined skills of the players - pill-popping has become pretty much passe.

"Back then it was just a different sport," Silas, who now plays for the Seattle SuperSonics, said recently. "A lot of the guys were hard drinkers and heavy poker players. They would stay out all night playing cards and such, and they had to pop an upper the next day in order to play.

"Basketball is more of a profession now. Guys are making astronomical salaries and they just aren't into staying up all night and all that. They don't need the pills.

"Early in my career I took an upper once, but I never have since. I thought I was performing, but I wasn't.

"The game is just too quick. Your mind has to be sharp and it can't be when you are taking all kinds of stuff...The nature of the game prohibits you from doing it."

Among athletes in the major American team sports, basketball players, on the whole, are perhaps the most physicallt gifted. They have to be able to run, jump and shoot. A high level of skill and concentration is required at every position.

"I know guys who have taken uppers to play and you can tell who they are and when they are on it by just looking at them," said one NBA player.

"A teammate of mine plays great one day and looks like horse c---the next. But who am I to tell him to stop if he thinks he needs it, that's his business."

"Basketballers just aren't into uppers," said trainer John Lally, who was in the American Basketball Association before coming to the Washington Bullets four year ago. "I don't think they can be. The side effects are so serious that they make you jittery for hours afterward.

"I've never had one player ask me for one, so if they are getting them, they are getting them from somewhere else. But you could tell by looking at a guy if he is something and I just don't know of any basketball players who are."

Adds Bullet Coach Dick Motta: "When I came in the league 10 years ago the players were popping pills. Uppers, I assume. But with all the bad publicity about drugs, the danger of malpractice suits against a team...Well, players are more aware, more careful, better educated.

"I just don't think the NBA has the problem it once did. As a league, we've probably done a better job than any pro sport of cleaning up our own act."

Many basketball players say they can understand a defensive lineman in football taking drugs to hype him up, "because his job is to kill the quarterback. We play a more civilized game," said one NBA player.

"I don't want to knock football, but a lot of those guys are animals. I think most basketball players aren't animals, but cocky S.O.B.s. They want to psych you out with their skill, not by trying to scare you half to death. The guys that I know who take junk regularly aren't too bright and there just aren't that many of them around."

The NBA has strict rules against trainers dispensing amphetamines or any prescription drugs, and they keep close checks.

"Everything I carry in my bag is inventoried by the league," Lally said. "Anytime a guy is even given a muscle relaxer, I have to document it."

The seemingly endless NBA season also makes amphetamine use unattractive. As soon as a game is over, it is forgotten. Then there is an early wake-up call the next morning for a game in another city.

"These players have such a tough time getting to sleep at night already," Lally said. "They certainly don't want to take something to keep them up longer."

While pro basketball players might not use many amphetamines, they are probably more attracted to social drugs, especially cocaine, than other athletes. So-called "recreational" drug use is reportedly widespread in the NBA, but players do not consider this a problem.

"Let's keep business seperate from pleasure," said one former player. "Basketball players may be more into that stuff, but it is because of the company they keep, and their life styles as individuals, not as players. Not that many guys are into 'coke' anyway, but the ones who are would be even if they weren't basketball players. It's just their style. It's a social thing with them. They travel in those circles, and they can afford it.

"I even know doctors who snort for pleasure, but when it's time to go to work, they leave it alone."

"As far as anything a player might take secretly - the joy of drugs, the jury stuff - the players know that I better not find out about it," said Motta. "If they're on the stuff, it's an unwritten rule of mine - I've never had reason to mention it before - that I'll never stand up for a guy who gets himself in trouble. I wouldn't be protective of him. In fact, I wouldn't say that I wouldn't be the one who notified the authorities. This is an area in which I am not a tolerant person."