Berkshire purchases often boost stocks. Shares of the steel maker traded as high as $151.32 on Friday, but closed at $145.48, up 0.8%. The S&P 500 fell 0.3%. The Dow Jones Industrial Average rose 0.1%.

In May, a 13F filing revealed that Berkshire Hathaway was buying mystery stocks. Now, at last, we know what they are.

At Berkshire Hathaway’s annual meeting earlier this year, Warren Buffett showed just how much of a fan he is of Apple’s CEO, Tim Cook. “Tim Cook has made Berkshire a lot more than I have made Berkshire,” Buffett said to laughter in the room. It was funny, but considering that Apple is Berkshire’s largest holding, I don’t think it was hyperbole.

The investment comes as UnitedHealth faces soaring medical costs, federal investigations, the fallout of the killing of a top executive and a cyberattack last year.

UnitedHealth (UNH) stock climbed 6.7% in Thursday afternoon trading after Warren Buffett's Berkshire Hathaway (BRK.B) (BRK.A) disclosed that it acquired a new stake in the health insurer during Q2 2025.

Buffett owned UnitedHealth shares before selling his stake in 2010, though his Berkshire Hathaway recently acquired shares.