(FORTUNE Magazine) – STANDING BEFORE A SMALL LECTURE hall in Chicago filled with nonstudents in September, Harvard Business School professor David Thomas drew laughter when he welcomed "one of the smallest groups in the world."

The group? Black board directors.

For the past few years black executives who sit on corporate boards have started coming together in the hope of leveraging their collective clout and ultimately increasing their numbers. This year the directors allowed FORTUNE to sit in on their hush-hush meeting.

The gathering was started informally two years ago by Charles Tribbett, managing director of Russell Reynolds, and John Rogers, CEO of Ariel Capital. At that first meeting there were just 30 directors; this year the summit drew 85 directors, including board members from Delta, Target, McDonald's, and Verizon. There are currently 185 black directors, and they hold a combined 321 of the 3,447 board seats available. This year's attendees included former Maytag CEO Lloyd Ward, who used to sit on the GM and J.P. Morgan boards and now sits on media company Belo's board; prominent D.C. civil rights attorney Weldon Latham, a member of the Deloitte & Touche board; and Hugh Price, former president of the National Urban League and part of the Sears board. Carl McCall, the former New York State comptroller who sits on the new Tyco board, also addressed the group. "This is a group of African Americans whom CEOs listen to," says Tribbett. "That's why developing this network is so important."

In an unguarded talk typical of the gathering, McCall made references to his abridged tenure on the board of the New York Stock Exchange after the compensation scandal surrounding Dick Grasso and urged the crowd to learn from his mistakes. He advised the directors to get "outside assistance" from accountants and attorneys. "You can't always count on management and the info they give you," he says.

The intense day and a half included hard-core networking (at one point Thomas forced directors who did not know one another into groups, giving them topics to discuss) and honest debate about general board issues such as CEO succession. The gathering stayed focused, though a few participants did have to sneak out for, well, board meetings.

Diversity was an underlying theme of the event, but talk went deeper than the typical "good business" rhetoric that is often bandied about in corporate settings. McCall told the group it was their obligation as black directors to always bring up issues of diversity in the boardroom. While some argued that they did not want to be typecast as the "black voice," others countered that such typecasting was inevitable. "It doesn't matter if we say anything or not--the conversation changes just by having us in the room," says Maceo Sloan, CEO of Sloan Financial Group and a member of the TIAA-CREF board. "That's why we have to get into those rooms." -- Cora Daniels