Google founders Larry Page and Sergey Brin have announced plans to sell millions of shares in the web search company they launched in 1998.
Google's founders are following the example of their staff
The pair each stand to pocket over $1bn (£535m) at current prices - and will still hold 27% of stock between them.
The proposed sale comes after employees and early investors in Google were given their first opportunity to cash in their shares earlier this month.
Google has warned that fiercer competition is set to hit sales growth.
And investors are waiting to see how the market on Monday reacts to the announcement.
Mr Page and Mr Brin, both 31, will sell their holdings over an 18-month period.
Google chief executive Eric Schmidt will also be selling about 15% of his holding.
Analysts say increasing the amount of Google shares in circulation may ease demand for stock.
Google's shares closed up 1.1% at $169.40 on the Nasdaq on Friday, but are down from highs of $201.60.
The shares were priced at $85 at the time of the flotation in August.
Restrictions imposed ahead of the flotation to prevent shares being dumped quickly onto the market were lifted on 16 November.