Hertz Global Holdings, facing a huge pile of debt paymentsand big bills to upgrade its fleet, is getting the bondmarket's version of sticker shock.

Refinancing costs are surging after more than a quarter of thecar-rental company's market value was obliterated in one week and agauge of its credit risk jumped to the highest since the financialcrisis. Those rising costs could effectively shut Hertz out of theunsecured bond market it has relied on for years to replenish cashand purchase cars. With interest expenses already topping half abillion dollars a year, Hertz may have to pledge more of its assetsto creditors to keep those costs from going even higher.

Some of Hertz's bonds are the year's worst performers in Bank ofAmerica Merrill Lynch's high-yield services index, with yieldshovering near 9%. The junk-rated company needs extra cash toupgrade cars and technology, but it would have to pay heftypremiums — yields of perhaps 10.5% — to get investors to buy anymore unsecured debt, said John McClain, a portfolio manager atDiamond Hill Capital Management. At these levels, creditors have toevaluate the company as if they might own it someday, McClainsaid.