Shares of Amazon.com Inc. (AMZN) dropped to a 52-week low Friday after the online retailer reported third quarter profits that tripled, but fell short of Wall Street estimates.

The Seattle-based online retailer reported net income of $54 million, or 13 cents per share, for the quarter ended Sept. 30. For the same period a year ago, the company had profits of $16 million, or 4 cents per share.

Net sales for the quarter were $1.46 billion, up 29 percent from $1.13 billion for third quarter 2003, and were especially strong in Europe and Asia. Excluding a $57 million benefit from changes in foreign exchange rates, net sales grew 24 percent over comparable 2003 figures.

Pro-forma earnings, which exclude stock-based compensation, operating expenses and other items, were $73 million, or 17 cents a share for the quarter, compared with $48 million, or 11 cents per share, for the same period a year ago.

Based on those numbers, Amazon missed Wall Street expectations by a penny per share, and also fell just short of revenue expectations. Analysts polled by Thomson First Call had predicted earnings between 15 cents and 20 cents, with a mean of 18 cents a share, on revenue of nearly $1.47 billion.

Amazon shares fell $4.87, or 12.3 percent, to close at $34.60 Friday on the Nasdaq Stock Market (search), below its previous 52-week low of $34.85.

Analyst Dan Geiman with McAdams Wright Ragen (search) called the quarterly numbers "a little bit disappointing."

"Investment in their infrastructure and technology, and lighter sales than expected, kind of contributed to it all," he added.

Amazon said that for its North American markets, sales were $816 million, up 15 percent from a year earlier. In its international segment, which includes the company's United Kingdom, German, French, Japanese and Chinese Web sites, sales were $646 million, up 52 percent.

Strong growth in its electronics and other merchandise segments also drove the company's revenue.

Despite missing expectations, chief financial officer Tom Szkutak said the company was happy with its performance.

"This was another solid quarter for Amazon.com," Szkutak said.

The company said it expects fourth-quarter net sales between $2.3 billion and $2.55 billion, up by 18 percent to 31 percent over fourth-quarter 2003.

The company's full-year guidance was virtually unchanged from prior expectations. Amazon said it expects sales of between $6.68 billion and $6.93 billion. Previously it forecast sales of between $6.63 billion and $6.94 billion.

"They're forecasting some reasonably conservative revenue guidance for next year," Geiman said. "I think they're going to continue investing in their infrastructure. You're going to continue to see them investing in the near term with expectations of driving longer term earnings and cash flows."

For the first nine months of 2004, Amazon earned $241.8 million, compared with a loss of $37.9 million for the first nine months of 2003. Nine-month net sales rose to $4.38 billion from $3.32 billion a year earlier.