SHANGHAI — Stephen Brown has "always been fascinated with the idea of a world's fair." Mary Schnack is a businesswoman hoping to make connections in Shanghai. Brian Greenberg has long dreamed of visiting China.

They're among thousands of Americans heading to the Shanghai Expo, which opened last weekend for a six-month run. Nearly 200 countries and dozens of corporations are participating, with pavilions and exhibits showcasing culture, tourism, technology and a theme of environmentally sustainable cities.

The Expo has not received a lot of publicity in the U.S. Seventy million visitors are expected to attend in all, but only 3 million to 5 million foreigners. Still, Americans who do plan to attend have great expectations and often very personal reasons for going.

Wan Wu, 63, was born in Shanghai and owns a Chinese grocery store in Quincy, Mass. He plans to attend the Expo later this month.

"I am always proud to be a Chinese-American who was born and who grew up in Shanghai," he said. "This is definitely a once-in-a-lifetime experience I do not want to miss."

Sam Roth, 17, a high school student from Oakland, Calif., will be attending the Expo in July as part of a summer camp to "learn about business in China."

She said she expects the most impressive aspect to be "the scale on which the Chinese do anything. ... That is the wow factor."

Greenberg, 53, a CPA from Cherry Hill, N.J., said he's long wanted to go to China, and "what adds to the trip is that the Expo will be there."

He added that "traditionally, a world's fair is where new technology has been introduced, and that's my expectation, to see something I've never seen before."

Jim Little, 66, an economics professor, is one of several faculty members from the Washington University in St. Louis going to the Expo. The school has a joint MBA program with a university in Shanghai.

He said that while this Expo has fewer "technological marvels" than past world's fairs, "it will be the biggest and best Expo in history," with countries participating not just to sell products, but to sell themselves as destinations. "Chinese tourism already has become an important aspect of tourism for many countries," he said.

"How seriously is this being taken by countries around the world? How are they going to present that?" she said.

Irene Natividad, 61, president of a Washington, D.C.-based organization called the Global Summit of Women, is taking an international delegation of 120 women to the Expo in late May, following a meeting in Beijing.

"China is the 21st-century global leader in the world's economy. I know they will put on a show that will exceed that of others in the same way that they did in the Olympics," she said.

Michael Berkowitz, 30, and his wife Debbie, 28, of San Francisco, decided to stop in Shanghai to see the Expo as part of a trip around the world. They spent Sunday at the fair, had fun and enjoyed the spectacular architecture of many of the pavilions. But they said the technology on display — such as touchscreens and 3-D and 4-D movies — didn't seem all that cutting-edge and was mainly a device for countries to showcase their achievements and cultures to the Chinese public.

"Twelve hours," Michael Berkowitz said, "was plenty."