Shares in Zynga, the maker of the online games FarmVille and Mafia Wars, have fallen 5% on their first day of trading.
The firm went public at $US10 a share on Friday, putting a $7 billion price tag on the company, making it the biggest internet initial public offering since Google in 2004, the BBC reports.
The stock rose as much as 10% in early trading on the Nasdaq before rolling back to close at $US9.50.