Warren Buffett added to Berkshire Hathaway's bet on Wal-Mart, increasing its stake in the retailer by 17 percent to 58.05 million shares during the first quarter.
The additional 8.57 million shares are worth about $658 million at the stock's closing price Thursday of $76.83.
Wal-Mart shares fell 2.4 percent in Thursday's trading after the company reported anemic sales growth and forecast disappointing earnings. It blamed bad winter weather.
With a total value of $4.46 billion, the Wal-Mart stake is probably being controlled by Buffett himself.
It is now Berkshire's fifth largest U.S. stock stake.
Buffett also added slightly to his company's fourth biggest holding. Berkshire's stake in IBM edged higher by 233,100 shares to 68.36 million shares.