Private equity firms use borrowed money to acquire companies that they hope to resell at a profit. It is no secret that fees charged to investors in private equity funds are high. Many investors view those fees as the cost of entry into a hot investment arena.

This year, the problem of hidden and possibly abusive fees at these funds has been brought to light in several articles in The Times. Many investors, for example, did not know that private equity firms could charge fees for monitoring an investment even after it had been sold. Neither did most investors realize that they were responsible for the payment of legal settlements if private equity executives were accused of wrongdoing. One reason investors are often in the dark in these matters is that the terms of the agreements they strike with the private equity firms are kept confidential, even from beneficiaries.

The S.E.C. declined to comment on the Freeman Spogli situation specifically, but Drew Bowden, director of the S.E.C.'s office of compliance inspections and examinations, said the increased scrutiny being brought to bear in the private equity industry is resulting in industry changes. “You see investors asking questions they didn’t formally ask before, insisting on certain terms and refusing certain terms,” Mr. Bowden said. “Advisers are also modifying their behavior and realizing the tolerance for certain terms is not there.”

Private equity firms oversee assets belonging to endowments, pension funds and wealthy individual investors. The firms typically charge these investors 2 percent of assets annually as well as 20 percent of any gains their portfolio companies generate. The investments are usually locked up for at least five years.

Historically, private equity funds have been stellar performers. But in recent years, their performance has dimmed; over the last five years, on average, they have lagged the returns of the broad stock averages.

Amid this decline, some investors have raised concerns about hidden fees levied by private equity funds. They include fees paid by the companies held in the private equity firm’s portfolio. The companies end up paying fees to the private equity firm for things like issuing debt or the oversight of portfolio companies, known as monitoring services.

Responding to investor demands, private equity firms now routinely reduce management fees charged to investors by the amount of these expenses, or some portion of them. These arrangements vary from firm to firm and range from offsets of 50 percent of fees to 100 percent.