Fenwick & West corporate partner Ted Wang has a simple explanation for why his firm decided to join the "Lean In" campaign launched earlier this month by Facebook chief operating officer Sheryl Sandberg in conjunction with the publication of her buzzed-about new book of the same name that aims to help women advance in the workplace.

"If Sheryl's involved, it's a good thing," he says.

Wang should know; Silicon Valley–based Fenwick is the firm that helped take Facebook public in 2012. He insists, however, that the involvement of a top executive at one of Fenwick's key clients was not the only draw. "We have a problem, and we think this will help us," he says, pointing to the fact that women represent half of Fenwick's incoming associate class, but only 17 percent of its partners and just one in 10 members of its executive committee.

Fenwick is one of five Am Law 200 firms among the more than 150 companies and organizations that have signed on as partners to Lean In, which encourages women to take control of their professional careers, in part by openly discussing the challenges they face both at home and at work. The other firms lending their names and support to the cause are Orrick, Herrington & Sutcliffe; Sidley Austin; Skadden, Arps, Slate, Meagher & Flom; and Weil, Gotshal & Manges.

As Sandberg, 43, explains in a video on the Lean In website, the campaign is based on the idea that to make real progress professionally, women need to talk with each other, as well as their male counterparts, to change the fact that "We don't sit at the table, we don't raise our hands, we don't let our voices be loud enough." Sandberg, who joined Facebook in 2008 from a position as vice president of global online sales and operations at Google, pushed the same message in a powerful 2010 speech delivered at a TEDWomen conference on why the business and political world has too few female leaders.

Although the Lean In movement does not specifically target the legal industry, there is ample evidence that large law firms are marked by significant gender inequality. Even though women have been entering law firms in almost equal numbers to men for years, they now make up, on average, just 15 percent of the equity partnership ranks at the nation's 200 largest law firms, according to a report issued in October 2012 by the National Association of Women Lawyers.

As The American Lawyer reported in its January issue, few women have made their way onto the highest-ranking management committees of the nation's largest firms. Senior reporter Amy Kolz found that the vast majority of Am Law 100 firms had no more than one or two women on such committees, with female partners making up more than a third of those bodies at only a handful of firms. (While women are better represented among the ranks of practice group leaders and office managing partners, many argue that such roles don't hold the real power in a firm).

Of the firms committing to Lean In, Skadden fared the best in the American Lawyer's January report, with 21 percent of its policy committee—4 out of 19 members—being women. Orrick's board at the time was 18 percent women (2 out of 11); Sidley's management committee was 10 percent women (1 out of 10) and its executive committee was 17 percent women (8 out of 48); and Weil's management committee had 18 percent women (3 out of 17). The lone women serving on Fenwick's executive committee, Kathryn Fritz, is the firm's managing partner.

Over the past few years, firms have done a better job of promoting women into their partnership ranks. So far in 2013, 35 percent of the 717 new partners The American Lawyer has tracked are women. Of the five Lean In firms, women made up a quarter of Weil's 10-partner class. In 2012, Skadden promoted five women among a class of 11 new partners, or 45 percent.

Representatives from the firms supporting Lean In say it's still too early to know exactly what form their involvement will take, but they welcome the chance to join the conversation. Carter Phillips, co-chair of the executive committee at Sidley Austin, said one of the draws for him was the potential to collaborate with industries beyond the legal sphere. "It's a broader network than we normally tap into" to discuss women's advancement, he says.

"I viewed this as just being one more opportunity to get people to talk about it, to share what works," says Orrick corporate partner Karen Dempsey, who got the firm involved after hearing about the movement from Silicon Valley entrepreneur Mari Baker a month and a half ago.

Adds Meredith Moore, Weil's global diversity director and social responsibility director: "Everything Sheryl Sandberg is talking about … is how do we accelerate the pace of change? I think the dialogue has been pretty stale for the past 15 years, but it seems there's a renewed energy around this conversation." Moore notes that Weil took its own stab at furthering that conversation within the past year by launching a new mentoring program that pairs one male partner and one female partner with a small group of female associates.

Ultimately, says Fenwick's Wang, the goal is "to really to get people involved. If we just put our name on it, it's useless."