Amazon CEO Jeff Bezos briefly became the world’s richest man in Forbes magazine’s tracking of wealth, as stock in his e-commerce company hit an all-time high.

Microsoft founder Bill Gates reclaimed the lead by Thursday afternoon, as Amazon’s stock fell nearly 1 per cent for the day to $US1046.

Amazon shares have been trading at a record high. They hit $US1083.31 about noon on Thursday. According to securities filings, Bezos owns about 80 million shares, or 17 per cent; those shares were valued at more than $US87 billion ($A109 billion) at the peak.

Bezos also owns The Washington Post through a holding company.

Forbes said Bezos’ net worth was about $US90.6 billion when the market opened on Thursday. Gates had $US90.1 billion.

Forbes said Gates would have been the undisputed leader had he not given billions of dollars away to various philanthropic causes.

Bezos issued a request for philanthropic ideas in a tweet in June, just before Amazon announced a $US13.7 billion deal for organic grocer Whole Foods.

The changes in Bezos’ fortune coincided with Amazon’s report of a 77 per cent decline in quarterly profit on heavy spending.

Shares fell another 2 per cent in after-markets trading as the company missed Wall Street’s expectations on profit.

Amazon said it earned $US197 million, or 40 cents per share, in the second quarter, down from $US857 million, or $US1.78 per share, a year ago.

Analysts surveyed by Zacks investment Research were expecting earnings of $US1.40 per share on revenue.

Revenue grew 25 per cent to $US38 billion, compared with $US30 billion a year ago.

But Amazon has long been known for investing the money it makes back into its businesses. For the second quarter, Amazon reported operating expenses of $US37 billion, a 28 per cent increase from a year earlier.

– AAP