Trulia’s stock starts with a bang, but it still has a ways to go to catch Zillow. Click on chart for interactive version.

The fascinating back-and-forth between Zillow and Trulia continues. After pricing its initial public offering last night at $17, Trulia shares are taking off in early morning trading, opening at $22 per share and trading now at more than $24. That’s a very healthy 40+ percent increase over the offering price. The IPO, as we reported yesterday, raised $102 million for the San Francisco online real estate company.

Not to be outdone, Zillow used Trulia’s public debut day to announce that underwriters of the company have agreed to purchase 419,818 shares of Zillow at $43, adding even more cash to the company’s books. The secondary offering has now  brought Zillow an additional $156.7 million, nearly double the amount of its IPO last year.

As we’ve noted in the past, this is one tech rivalry that’s certainly been fun to track over the years. Things heated up last year when Trulia CEO Pete Flint told us that it “is really just a question of time before we overtake them,” referring, of course, to Zillow.

“We started as four guys in a student library, and they started with 150 employees and an army of vice presidents. So, we are quite different in how we think about business,” Flint added.

Zillow, founded by former Expedia executives Rich Barton and Lloyd Frink, usually has kept pretty mum when it comes to Trulia. But that changed last week when Zillow sued Trulia for patent infringement over its home valuation tool, calling it a “blatant and ongoing copying of Zillow’s innovative approach to home valuation.”

Zillow’s stock has been on the rise this year. Click on chart for interactive version.

The timing of that suit was interesting, coming just as Trulia was talking with investors about its IPO.

Now, in addition to fighting in the courts, Zillow and Trulia can battle it out on Wall Street. Zillow, which is bigger in almost every metric, holds the lead in that battle for now.

Its stock, which is holding steady today, is now at $45.59. That’s more than double the $20 IPO price, currently giving Zillow a market value of $1.34 billion.

UPDATE: Trulia closed its first day on Wall Street at $24 per share, up 41 percent from the $17 offering price. Zillow’s closed near a 52-week high of $46.17.

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