CAMBRIDGE, Mass. (AP) _ B.F. Skinner, the psychologist who popularized behavior modification, is facing his approaching death by leukemia with no regrets, a fitting end to a life he claimed was governed by rational rules.

Skinner, 86, is preparing what may be his final work, a defense of controversial research that explored the uses of positive and negative reinforcement to improve human behavior.

''I will be dead in a few months,'' Skinner said with a laugh. ''But it hasn't given me the slightest anxiety or worry or anything; I always knew I was going to die.''

For years, Skinner has endured a battering by many American psychologists who scorned his belief that behavior could be engineered to make society better. Not everyone will accept his final work, he said in a recent interview.

''I'm writing a paper which is my summing up of what psychology is all about and attacking cognitive psychologists,'' Skinner said. ''The cognitive psychologists won't like it, but that doesn't bother me at all.''

Cognitive psychology emphasizes the unconscious structures of the human mind, rules for the brain's operation that can't be explained by conditioning.

Skinner's principle of ''operant behavior'' holds that even seemingly spontaneous action is a response to rewards and punishment. People don't shape the world, he has said. The world shapes them.

On Friday, Skinner is to be honored by the American Psychological Association in Boston.

The appearance will be tricky. The cancer has decimated Skinner's immune system, and visitors to his Cambridge home must wash their hands before meeting him.

''They're going to smuggle me up on the stage and then take me right back out,'' Skinner said. ''I won't go to a reception and shake anyone's hands.

''I suppose,'' he added with a chuckle, ''I could show up with rubber gloves on.''

Burrhus Frederic Skinner (B.F. to the world, Fred to his friends) grew up in Susquehanna, Pa., and spent most of his career at Harvard University, where he applied his observations of animals to the motives and manipulation of human conduct. He retired from the faculty in 1974.

Skinner argued that ''behavioral technology'' could be put to work to create a world free of overpopulation, war and pollution.

In ''Walden Two,'' published in 1948, he described a tightly controlled Utopia in which people are motivated by positive and negative reinforcements. The novel was required reading for many college students in the 1960s and 1970s.

In Walden Two, everyone is happy. People don't know the meaning of envy and jealousy. Buildings are communally owned, and everyone helps out with chores.

Many psychologists found Skinner's Walden to be a tyrannical place - others said it was bland. But his application of the ideas of the Russian physiologist Ivan Pavlov have left an indelible stamp on American society.

''We now know that many principles govern human behavior, not just 'operant behavior,' but that doesn't diminish his importance,'' said Jerome Kagan, chairman of the Harvard psychology department.

Operant conditioning is used every day by parents, Kagan said, ''every time they praise a behavior they want and punish one they don't want.''

To his regret, Skinner may be best remembered for teaching pigeons to play pingpong, using the Skinner Box. The pigeons pressed buttons or levers to receive food in return for doing what the experimenter wanted them to do.

A Life magazine photograph of the pigeons hangs in Skinner's wood-paneled study in his home. Nearby is a signed portrait of Pavlov, whose experiment showed dogs could be conditioned to salivate at the ring of a bell.

Skinner's frame is lean but otherwise he shows little sign of illness. His snow-white hair is combed back from an expansive forehead and his blue-gray eyes sparkle when he discusses his work.

He laments the search among cognitive psychologists for an ''inner creator'' responsible for human behavior, likening them to creationists who scorn Darwin's theory of evolution.

Skinner compares the search for an inner self to the search for God. Skinner doesn't believe in God, either.

And how does Skinner want to be remembered?

''Somebody asked my daughter recently what she remembered most about me,'' he says. ''It was very strange. She said I used to come and put her to bed and talk with her, and I'd take her hand and there'd be tears in my eyes.''

''I'd hate to have people say he's the man who taught pigeons to play pingpong.''