Amazon ( AMZN), whose shares have slumped 41% this year amid concerns about rising costs and competition, today said it would buy back as much as $500 million worth of its stock over the next two years.

Amazon, the No. 1 Internet retailer, has about 418.9 million shares outstanding, according to data on Yahoo! Finance.

Wall Street, which has questioned some recent Amazon moves including entering the low-margin grocery business, greeted the news favorably, sending the company's shares up 36 cents to $28.39 early Monday.

If you liked this article you might like

Google Grapples With YouTube

Google Grapples With YouTube

Fox Aims at Fantasy Crowd

Fox Aims at Fantasy Crowd

Amazon Downloads Unveiled

Amazon Downloads Unveiled

Google Gains as Ads Slow

Google Gains as Ads Slow

Google Rolls Out News Search

Google Rolls Out News Search