Mark Zuckerberg has tipped a bucket of ice water over his head on film and nominated Bill Gates to perform the stunt next.
The Facebook founder accepted the Ice Bucket Challenge - a viral ALS Association initiative - from New Jersey governor Chris Christie.
He also nominated fellow Facebook parter Cheryl Sandberg and Neflix founder and CEO Reed Hastings.
The ALS Association has reported raising more than $4 million (£2.4m) since 29 July thanks to the campaign, which has seen a host of big names take part so far.
The rules go that if the challenge is declined, then the nominated person has to donate $100 to the charity.
Macmillan Cancer support has adopted the idea in the UK, but has asked participants to donate £3 when the dare is completed.
Microsoft CEO Satya Nadella has done it, but will Gates?