(Adds data from NAR beginning in paragraph 13)

By Julie Haviv

NEW YORK, Feb 12 (Reuters) - Prices of existing U.S. single-family homes dropped a record 12.4 percent in the fourth quarter from a year earlier to the lowest level since 2003, the National Association of Realtors said on Thursday.

The NAR said distressed sales, which includes foreclosures, accounted for 45 percent of transactions in that quarter, dragging down the national median price of existing single-family homes to $180,100.

The median is where half sold for more and half sold for less, and it was the lowest since the second quarter of 2003 when it was $177,900.

At the same time, existing-home sales rose in only six states from the fourth quarter of 2007, the NAR said.

In the fourth quarter, prices for single-family homes declined in 134 out of 153 metropolitan statistical areas from the same period in 2007, pulled down by active sales at the lower end that were driven by foreclosures, the NAR said.

The NAR said one metropolitan area was unchanged and 18 metropolitan areas reported price gains. The NAR's data on metro area home prices dates back to 1979.

NAR President Charles McMillan, a broker with Coldwell Banker Residential Brokerage in Dallas-Fort Worth, said homes and neighborhoods minimally impacted by foreclosures have moderate prices changes.