(FORTUNE Magazine) – Interested in putting a few thousand dollars into hot growth companies in Eastern Europe? Or in one of those richly rewarding private placements of stock that Saudi Arabian princes seem so fond of? Up to now, such investments have been the stomping ground for institutions and the very wealthy. Locked out by the rules governing open-end mutual funds, most investors could only peep through the knothole. Soon ordinary fund buyers may be able to invest in virtually anything the big guys do. The Securities and Exchange Commission is preparing to relax one of its toughest strictures and let investment companies offer so-called interval funds. Today open-end funds, which account for the overwhelming majority of mutual funds, must keep at least 85% of their assets in readily marketable securities. The rule ensures that the funds are able to pay any investor who decides to redeem shares, but forces fund managers to concentrate their assets in mainstream stocks and bonds. Investors interested in more rarefied investments can buy closed-end funds, but many people shy away from them because the shares cannot ordinarily be redeemed from the fund manager. Instead, they trade on stock exchanges like equities, and when the time comes to sell, investors aren't always able to realize the full value of the underlying assets. Interval funds would gain the investing flexibility that other open-end funds lack by limiting the customer's redemption right. An investor who wanted to redeem shares would have to notify the fund well in advance -- 30 days, say -- giving the manager time to come up with the cash. The extra weeks would free the manager to invest in markets that he'd otherwise have to pass by, says Donald Pitti, president of Seligman Financial Services in New York City. Companies such as Fidelity Investments and John Hancock are waiting for the SEC to establish interval fund ground rules. The SEC published proposals last year; experts are guessing that formal guidelines will appear by September. Pitti, meanwhile, is trying to get a jump on the competition. He has applied for special permission to launch what would be called the Seligman Henderson Emerging Companies Interval fund. It would focus on promising small- capitalization growth stocks in Europe and the Pacific Basin; investors would be allowed to redeem shares on only one day in each quarter and would have to notify the manager a month in advance.