On Sept. 13, 1982, Princess Grace of Monaco was killed when the car she was driving somersaulted over a cliff. Her daughter, Princess Stephanie, who was with her, had not spoken on the record about the crash until an interview with author Jeffrey Robinson for his book, ''Rainier and Grace: An Intimate Portrait.'' She recounts the accident in this excerpt from the book.

At about 9 a.m., on Monday, Sept. 13, 1982, Princess Grace of Monaco woke her daughter, Stephanie. They had tickets for a train to Paris, where Stephanie, 17, would start school on Wednesday.

While Grace was getting ready to leave for the palace, her chauffeur brought the 11-year-old metallic green Rover 3500 out of the garage and parked it in front of the house at Roc Agel, the royal family`s farm, in the hills above Monaco.

When Grace came out of the house, her arms were full of dresses which she spread flat across the rear seat of the car.

A maid followed with other dresses and large hat boxes, and together they filled the rear seat.

Then she called for Stephanie.

Grace`s chauffeur was standing by the car, ready to drive the two of them to the palace.

Grace didn`t much like driving and didn`t do a lot of it, although she liked the Rover. There wasn`t a lot of mileage on it because she didn`t use it much. Still, she always insisted it be well maintained. It hardly, if ever, went any farther from the palace garage than Roc Agel. And even then it usually was driven by a chauffeur.

Now, however, with the back seat covered, there wasn`t room enough for Grace and Stephanie and a chauffeur.

Grace told her chauffeur that it would be easier if she drove.

He said that there was no need for that. If she left the dresses there, he would drive her down and then come back for the clothes.

She said, no, please don`t bother, she would drive. He kept trying to persuade her, but Grace insisted.

So Grace got behind the wheel, and Stephanie climbed into the passenger seat. At about 10 a.m. they pulled away from Roc Agel.

The road from the farm winds down the hill and into La Turbie. The road from there down to the Moyenne Corniche, which takes you into Monaco, is called the D37. Approximately 2 miles from La Turbie, there is an especially steep bend where you have to brake very hard and steer carefully to follow the road 150 degrees to the right.

Grace missed that turn.

The Rover slammed into the small retaining wall and went through it. The car somersaulted as it crashed 120 feet through branches of trees, careening off the slope, tossing Grace and Stephanie around inside.

The accident that claimed the life of the former Grace Kelly captured the attention of the world. Nearly 100 million people watched the funeral of the former American movie star on Saturday, Sept. 18: Her husband, Prince Rainier, in his uniform, shattered with grief, his oldest child, Caroline, veiled in black, reaching out to touch him. His son, Albert, walked at his side, holding his father`s arm.

Stephanie, the youngest of Grace and Rainier`s three children, was not present at the funeral. Still hospitalized for minor injuries from the accident, she wasn`t told of her mother`s death until two days after the crash.

Caroline is the only member of the family to have discussed with Stephanie what happened in the car that morning.

''Stephanie told me, `Mommy kept saying, I can`t stop. The brakes don`t work. I can`t stop.` She said that Mommy was in a complete panic. Stephanie grabbed the hand brake. She told me right after the accident, `I pulled on the hand brake but it wouldn`t stop. I tried but I just couldn`t stop the car.` '' Stephanie, now 24, says she has never discussed the accident with her father or brother. Some people close to the family say they think that Stephanie has since blocked the accident out of her mind, that she remembers nothing of what happened.

This is not the case, she said in a taped interview.

''I remember every minute of it,'' she says, trying to retain her composure. `It`s only in the last few years that I`ve been starting to cope with it. I had some professional help and especially in the last eight months I`ve been learning to deal with it. I still can`t go down that road, even if someone else is driving. I always ask them to take the other road. But at least I can talk about it without crying. Although it`s hard for me to get it out in front of my dad. As far as I`m concerned, I can live with it. But I still can`t talk to my dad about it because I know it hurts him and I don`t want to do that because I love him.''

Black out at the wheel

Family members recall that Grace was tired at the end of that busy summer. They remember her being irritable, suffering from high blood pressure (later published reports quote her doctors as saying that she did not have high blood pressure) and going through menopause.

''She wasn`t feeling too well,'' Caroline confirmed. ''She was incredibly tired. The summer had been very busy. She hadn`t stopped going places and doing things all summer long. She`d done too much. She never mentioned it or complained about it though. But she wasn`t in great form.''

Somewhere along the road Grace complained of a headache, Stephanie said. It continued to bother her as they headed down the hill. Then suddenly a pain shot up through her skull.

For a fraction of a second she seemed to black out, Stephanie recalls. The car started to swerve.

When she opened her eyes she appeared to be disoriented. In a panic, she jammed her foot on the brake. It appears now that she probably missed the brake and hit the accelerator instead. A witness to the accident said that he was 50 yards behind the Rover, nearing that very steep, sharp curve, when he saw the Rover swerve violently, zigzagging across both lanes. Then the car straightened out and shot ahead very fast. He knew the road and knew that the bend was coming up and, in those two or three seconds when he didn`t see any brake lights on, he realized what was going to happen.

Stephanie says she`ll never know for sure if her mother mixed up the accelerator and the brake pedal or just didn`t have the use of her legs. But when the police investigated the accident and checked the road, there were no skid marks.

Neither Grace nor Stephanie was wearing seat belts.

`Call my father at the palace`

The gardener who heard the car crash onto the property where he was working said in numerous press interviews that he pulled Stephanie out of the driver`s window, giving the impression that Stephanie had been driving.

However, Stephanie recalls it differently.

''I found myself huddled under the space below the glove compartment. I lost consciousness as we fell down. I remember hitting the tree and the next thing I remember is waking up and seeing smoke coming out of the car. I thought the car was going to blow up.