At Los Angeles' gay pride parade June 8, a local radio station had a float emblazoned with a banner that read, "Welcome to the hell that is marriage." The message was a cheeky nod to the May 15 California Supreme Court ruling legalizing marriage for same-sex couples, but it typified how quickly some segments in the business community are gearing up for same-sex nuptials, which began Monday evening.

Gay and lesbian couples are sure to be ecstatic on their wedding days, but the ones shedding the most tears of happiness may be California's wedding and honeymoon vendors. Will a change in law mean a bull market for big fat gay weddings? The Williams Institute at the U.C.L.A. School of Law thinks so. The think tank released a study June 9 showing California's $6 billion-a-year wedding industry will get an infusion of $683 million over three years in direct spending by same-sex couples.

Based on numbers in Massachusetts, where it has been legal for resident gays and lesbians to marry since 2003, the Williams Institute estimates roughly half of California's 102,000 domestic partners will get married, while another 68,000 couples from outside the state are expected to come and celebrate their nuptials. The Institute thinks same-sex marriage should generate 2,200 jobs in California, bring in $8 million in marriage-license fees, and increase sales and occupancy tax revenues by $55 million. A 2005 study showed that if same-sex marriage was legalized nationally, the wedding industry could generate another $2 billion annually.

That's peanuts for the overall industry, since 2.4 million straight couples get married each year and spend on average $20,000, racking up a total of $72 billion, according to bridal website theknot.com. But the potential for a deep-pocketed, underserved market coming online in an economy where more straight couples may be thinking of pulling back their spending is undoubtedly attractive to vendors.

The impact on California and the rest of the country could be significant, says Betsy Stevenson, an assistant professor at the Wharton School who studies the tax implications of marriage. She compared marriage in the Golden State today to Nevada 60 years ago, when that state's lax divorce laws made it a destination for couples looking to split. The revenue Nevada brought in encouraged other states to change their divorce laws. "Once California starts making money, other states will want to get into the game," Stevenson said.

San Francisco first saw the economic potential back in 2004. Thousands of same-sex couples were married out of City Hall around Valentine's Day before the state put the kibosh on the renegade licenses and began litigation that ultimately led to this year's decision. Businesses in the city, which for years have catered to informal commitment ceremonies, were struck by a "Flowers from the Heartland" phenomena, a movement in which well-wishers ordered wedding flowers for same-sex couples they didn't know. Thousands of bouquets were distributed randomly to the throngs of couples waiting to get married, a boon to florists in the city.