San Francisco police are hoping surveillance pictures will lead them to the criminal and the bike.
They say a man stole it from a gated apartment garage.
He's described as white, 5'8", about 25 to 30 years old, with a shaved head.
The bike is distinctive because the passenger sits in the front and the person in the back steers.
There are only three similar bikes in San Francisco and only 450 in the United States.