The 16-year-old Olympic debutante toot the gold in 16.225 points, followed by her compatriot Nastia Liukin in 16.025. China's Cheng Fei settled for bronze in 15.950 points.

Johnson, 16, winner of three gold medals in last year's world championships, sailed to her first Olympic gold with smooth tumbling and twists and a solid landing.

Reigning beam world champion Liukin presented a flawless routine but her difficulty value of 6.6 points, 0.4 points lower than Johnson's, earned her a second place.

"I am so proud because it (beam) is my favorite apparatus. I gave my heart and soul and I did my best routine today. I worked so long for this, " said Johnson after the competition.

"It's the perfect ending to my Olympic experience," she said. Before the beam gold, she had already pocketed three silver medals, one for all-around, one for floor exercise, and another for team event.

She said she did not see the mistakes of the Chinese gymnasts on the beam. "Anything can happen though-like nerves, and it's the last day and it's beam a long time, and we've worked hard. I feel for them, but I still think they did a great job."

China's Li Shanshan, the beam silver medallist in last year's world championships, lost her chance for a medal after she missed her step and almost dropped from the apparatus, following a tumbling combination.

Cheng Fei, a two-time Olympian, got her second bronze medal at the Beijing Olympics due to major wabbles during her routine.

The home crowd applauded to cheer them up when the tearful Chinese pair hugged each other for comfort.

"It is really difficult for me to shift my mind. I cried a lot yesterday and I was very depressed. I think I lost my spirit, my whole body was empty because I had been so successful ever since I entered Gymnastics," said Cheng.

The 21-year-old, deemed as the core figure of the Chinese gymnastics women's team, was dealt a big blow when she failed her two speciality apparatus.

The reigning vault champion ended with a bronze after a failed second vault. She finished 7th in floor exercise, her another favorite.

"I have never been faced with a big failure like that. I have thought about having problems in my performances, but never thought it could be so serious."

"Of course I have regrets, because I had the chance to win two gold medals but failed. I want to hold on to the next Olympic Games, but I think it may be really hard for me. I was at the top this year, but the rules of gymnastics will be changed after the Beijing 2008 Olympic Games. I never know what will happen," she said.

Cheng said she and her teammate Li made the same mistake. "She prepared very well before the competition, but everything can happen in just a second. The moment we are not calm, everything will be ruined."