(MONEY Magazine) – In the midst of your annual tax-filing frenzy, you've probably noticed those little boxes on your state income tax form asking you to donate from $1 to your entire refund to a special fund. Thirty-nine states and the District of Columbia give taxpayers the chance to support causes as wide-ranging as organ transplants and wildlife conservation. And in 1996--the latest year for which data are available--Americans ponied up $23.4 million for charity by way of their state tax returns. But where exactly does your money go?

Good question, and one that we found devilishly hard to answer, even after we called tax officials in half a dozen states. In some cases, the funds go to an easily identifiable charity, such as the U.S. Olympic Committee. At other times, the money takes a more circuitous route. A donation for breast cancer treatment might go from the tax department to the health department before working its way to a charity that's not even named on your tax return. Want to know more? Try your state's annual report (usually available from the department of revenue).

Just because it's tough to follow the money, should you hesitate to give? No, say experts such as Daniel Borochoff, president of the American Institute of Philanthropy, a Bethesda, Md. charity watchdog. If a cause appeals to you, go ahead and donate. But save your large gifts for a charity with finances you can track. Finally, even if your state's checkoff goes through a government agency, your gift is still deductible--on next year's tax return.

--BEVERLY GOODMAN