The initial public offering of shares in Chinese Web search engine Baidu.com Inc. seemed to have it all: exposure to China's booming consumer sector, a pure play on a hot industry, and a chance to own what is commonly referred to as the Chinese Google.

The result was the best U.S. stock debut in more than five years, according to Thomson Financial. Baidu's American depositary shares closed at $122.54 on Friday, rising 354 percent on the Nasdaq Stock Market from its offering price, the biggest first-day gain since telecom-equipment provider Finisar Corp. jumped 357 percent in November 1999 -- during the final chaotic months of the Internet stock-market boom.

And to many observers Baidu's lofty share price looks like another case of speculative excess. The Chinese company, which estimated it had net income of $1.5 million for the three months ended in June, now has a market capitalization of about $4 billion.

"This is a good company but a very bad stock right now," said Donald Straszheim, head of Straszheim Global Advisors, an economic and financial-markets consulting firm that focuses on China. "People in our Beijing office use Baidu and really like it. But I'd be surprised if the stock is even at the same level a year from now."

By more than quadrupling from its offering price, Baidu's stock has exceeded the percentage rise that Google Inc. has experienced since its debut last year. Baidu was able to achieve that mammoth gain in one day, from its late-Thursday offering price of $27. Google closed Friday down 1.8 percent at $292.35.

"I had this rated very highly at an A-plus-plus, but I thought this would go up 10, maybe 20 points at the most. This is something else," said Sal Morreale, who tracks IPOs for Cantor Fitzgerald in Los Angeles.

Baidu's spectacular one-day rise comes at a time when the IPO market is in an upswing, with more companies priced above their expected ranges and most closing higher on their first day of trading.

But with few other Internet-related public offerings on the horizon, analysts said Baidu's debut probably is a one-time event rather than a renewed mania for technology stocks. Indeed, on the surface at least, Baidu offers exposure to certain hot investment themes that few companies can match.

While most of the popular publicly traded Chinese companies are infrastructure plays in sectors such as energy or telecommunications, Baidu offers a direct link to the increasingly sophisticated Chinese consumer. In its IPO prospectus, Baidu cites estimates that the number of search-engine users in China would rise to 187 million by 2007, from 115 million today. The Beijing-based company commands about 45 percent of that business -- nearly twice the market share for Google, China's second-most-popular search engine.

Yet there is considerable long-term uncertainty about the largely advertising-driven Internet-search business model in China. "It is very early," said William Bao Bean, an analyst in Hong Kong for Deutsche Bank Securities. "It will take us a while to figure out what the size of this market really is."

Moreover, Baidu could run into legal trouble with Chinese authorities, which maintain strict, unpredictable control over the content of all media -- even the music industry, for services that enable users to search for links to pirated MP3 files. About 20 percent of the searches on Baidu are for music files.

Some analysts suggest that many investors viewed Baidu's IPO as a second chance for those who were unable to participate in Google's IPO. Many institutional investors were left out of that offering when Google took the unusual step of holding an online auction so that more small investors could participate. Further fueling interest was speculation that Google, which has a 2.6 percent stake in Baidu, has attempted to acquire the Chinese company.

The surge in Baidu's stock price brought with it questions about whether lead managers Goldman Sachs Group and Credit Suisse First Boston failed to price the IPO appropriately, even though the underwriters had raised both the size of the offering and the price. Mr. Straszheim of Straszheim Global Advisors suggested that Baidu could have raised twice the money by issuing the shares at $54, instead of $27, or it could have given up half as much ownership for the same amount of capital. "This is a clear case of the bankers' being asleep," he said. Goldman Sachs and CSFB declined to comment.

Robin Li, Baidu's 37-year-old chief executive and co-founder, said his company had "done a very successful IPO. We're excited that U.S. investors can share in the growth of our opportunities." The IPO raised $86.6 million for Baidu and brought in the company $77 million after fees.

Some global investors who stayed away pointed to the poor performances of certain other Chinese stocks. Despite China's locomotive economic growth, some Chinese companies have suffered from bad management, poor earnings and sometimes shabby treatment of foreign shareholders.

"With Chinese stocks, if you can find a winner, you've been lucky," said Dennis Gaughan, a managing director at Big Sky Capital, a Santa Monica, Calif., hedge fund that passed on the deal.

But most don't fare that well. For the 23 Chinese technology companies that have priced IPOs on the Nasdaq since 2000, the median first-day gain was 13 percent, according to Mr. Straszheim. After a month, that gain stood at 9 percent, and one year later, the median performance was a decline of 34 percent.

Even at its offering price of $27, Baidu looked expensive at about 42 times its trailing net revenue. Google, by contrast, is valued at 19 times trailing revenue.