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.
Berkshire added a new 11 million share stake in Verizon during the quarter, but the current value of the holding is around $527 million, indicating the purchase was made by one of Berkshire's portfolio managers.
Even so, the vote of confidence helped lift Verizon shares by 1.7 percent in after-hours trading.
According to a filing with the SEC of Berkshire's holdings as of March 31, there were three big percentage cuts.
Compared to the end of 2013, its General Motors holdings fell by 25 percent to 30 million shares.
It also reduced its stake in Phillips 66 by 64 percent to 9.7 million shares.
In addition, its Starz holdings fell 58 percent to 1.9 million shares from 4.5 million shares.
At the same time, Berkshire's reported holdings of Liberty Global increased to 14.7 million shares, split between Class A and Class C shares, from 2.9 million.
Its DirecTV stake dropped 5 percent to 34.5 million shares.
The total market value of the reported portfolio was $105.8 billion as of March 31. That's up about 1 percent from $104.8 billion as of December 31.
The filing did not indicate that any holdings were being kept confidential. That sometimes happens with the SEC's permission when Berkshire is accumulating a stake and wants to keep copycats from driving up a stock's price.
—By CNBC's Alex Crippen. Follow him on Twitter: @alexcrippen