Billionaire investor Warren Buffett has donated $US1.6 billion to the charitable foundation created by Microsoft founder Bill Gates and his wife Melinda.
In all, he donated shares worth $US1.93 billion to five foundations.
The BBC reports the rest went to foundations set up in the name of Mr Buffett's late wife, Susan, and their three children.
Mr Buffett, who owns the investment company Berkshire Hathaway, pledged in 2006 to give away 99% of his wealth.
This year's donation is higher than the figure of $1.5 billion donated in 2009 because Berkshire Hathaway has improved its performance.
Mr Buffett is a trustee of the Gates Foundation, which supports projects including polio eradication, micro finance and university scholarships.
The Gates Foundation employs 830 people and spent $US3 billion last year.
The Susan Thompson Buffett Foundation provides scholarships for American college students.
Mr Buffett still holds about $US43.9 billion of Berkshire stock, or 23.3% of the total outstanding, according to documents filed with the US Securities and Exchange Commission on Friday.
In 2006, Mr Buffett made the largest philanthropic donation in US history, giving $US37 billion to the Gates Foundation.
In June, he and Mr Gates called on American billionaires to pledge at least half their wealth to charity.