Zillow Inc. (Nasdaq: Z) shares gained 19.9% to $31.49, a day after the online real-estate information provider reported its first quarterly financial results since going public in late July. Volume for the stock came in at 436,000 shares, just nosing out its full-day average.

A news release posted August 24 reported quarterly revenues increased 116% to $15.8 million from $7.3 million in the second quarter of 2010.

Marketplace revenues increased 269% to $9.7 million from $2.6 million in the second quarter of 2010. Display revenues increased 30% to $6.1 million from $4.7 million in the second quarter of 2010.

GAAP net income for the second quarter 2011 was $1.6 million, compared to a net loss of $2.0 million in the same period a year ago and a net loss of $0.8 million in the first quarter of 2011.

Said CEO Spencer Rascoff in the same piece, “The second quarter was outstanding for Zillow® with record revenues, traffic and mobile usage. It marks our first profitable quarter on a GAAP net income basis and our fourth consecutive profitable quarter on an Adjusted EBITDA basis. We’re extremely pleased with our progress and rapid growth, yet we believe we’ve only scratched the surface of our opportunity.”

The Seattle-based Zillow calls itself the leading real estate information marketplace, providing vital information about homes, real estate listings and mortgages through its website and mobile applications, enabling homeowners, buyers, sellers and renters to connect with real estate and mortgage professionals best suited to meet their needs.