The news of the Reserve's Primary Fund "breaking a buck," which means its investors risk not getting their full principal back, was notable in many ways.

The Primary Fund is a money market mutual fund or "money fund." Money funds invest mostly in securities that mature in 90 days or less. Generally, their managers use special accounting procedures to keep the share price at $1. But this fund's share price fell below $1 when an issuer of one of its debt obligations, Lehman Brothers Holdings, defaulted.

The event, which sparked concerns over the solvency of other money market mutual funds, triggered the U.S. Treasury Department to announce a temporary $50 billion program to guarantee payment for the U.S. money market mutual fund industry.

The New York-based Reserve Management Corp. is credited with setting up the nation's first money market mutual fund. In fact, one of us spoke with the company's founder and chairman, Bruce Bent, within the last few months.

Ironically, the conversation dealt with the issue of disclosing exactly what securities are contained in money market mutual funds.

So many people hear the term "money market fund" and don't realize that there can be many types of securities in them. Of course, based on their contents, some money funds are apt to be riskier than others. By contrast, a "money market account," or a savings account at a bank, is FDIC-insured.

Mr. Bent was very outspoken on this disclosure issue. Contrary to many in the mutual fund industry, he totally favored disclosing the contents of his funds. In fact, he stressed that he listed the updated contents of his funds daily on his company's Web site.

"They're afraid of publishing what they own because they don't want to be caught with their pants down," Mr. Bent said, referring to his money market mutual fund competitors. "I sincerely hope [rule makers] don't force them to do it, because then I continue to remain unique."

It has become evident in the last several weeks as the federal government has had to take an active role in bailing out many of our largest financial institutions, that we do need better investment disclosure.

Nobody should be investing without having a clear understanding of exactly what an investment is, what's inside it, the terms, fees, risks and possible conflicts of interest.

Armed with this information, at least you can make active and rational decisions about whether to invest.

The Securities and Exchange Commission has indicated that it is concerned over the issue of disclosure. But right now, it's too busy dealing with funds already holding troubled securities.

Mr. Bent, despite the misfortune currently plaguing his money fund, was ahead of his time in calling for disclosure. Other funds since have begun disclosing their contents.

But unfortunately, even with full disclosure, you still have some forces working against you if you want to invest.

One is that there always can be some surprises in spite of disclosures. Who would have guessed that $785 million of debt securities issued by a company a big as Lehman Brothers Holdings in a money market mutual fund suddenly would be valued at zero? That's why diversification is so important.

Then there also is the risk that investors, despite all the information that is disclosed to them, won't take the time to read it.