As president of the University of Miami, Donna E. Shalala answers to dozens of trustees, many of whom are captains of industry. But two of those board members also answer to her. Ms. Shalala's uncommon role reversal is a product of her lucrative service on the boards of two different companies headed by members of Miami's Board of Trustees. In effect, her role as a director at a national medical group and at a home-building empire places her in the position of functioning as her bosses' boss. While corporate board service is not uncommon for university presidents, Ms. Shalala is among a handful of college leaders who collect hundreds of thousands of dollars each year as directors for companies that are headed by or employ university trustees. Such board service is fraught with potential conflicts of interest because a university president may be disinclined to question or oppose an industry executive who has a say in his or her continued employment and compensation. So, too, may a university trustee's judgment be clouded in evaluating a president who has influence over the trustee's professional endeavors. Shirley Ann Jackson, president of Rensselaer Polytechnic Institute and one of the nation's highest-paid college leaders, also serves on the board of a company where institute trustees hold executive positions. Ms. Jackson's $1.4-million in earnings from six corporate boards in 2010 was higher than such earnings by any other president examined by "The Chronicle." Given the real or perceived conflicts that may arise, presidents would be well advised to decline directors' positions on the boards of companies that employ or are run by university trustees. Presidents who serve on corporate boards have come under increased scrutiny in recent years, as some faculty and company shareholders question whether a college leader can simultaneously fulfill the duties of running a university and helping to guide a publicly traded company. Add to those concerns skepticism about whether a company's profit-making ambitions are philosophically aligned with a university's stated mission, and some college chiefs have opted to avoid the whole hornets' nest that corporate directorship has become. The flip side of the argument, as many presidents who serve on boards are inclined to point out, is that college leaders can learn valuable management lessons in corporate boardrooms, while also imparting their own wisdom from academe.