Tampa Bay area home prices fell 0.6 percent in May, according to a Standard & Poor's/Case-Shiller 20-city home price index released Tuesday.

Nationally, prices rose 1 percent from April to May in the 20-city index.

The bay area, along with Detroit and Las Vegas, were the only three cities where prices fell. The index does not list prices in dollar figures.

In contrast, data from real estate agents shows that the median price of single-family homes rose or remained flat in the Tampa Bay area from January through June, the longest stretch without a monthly decline since 2006.

In those six months, the median selling price of single-family homes - including conventional, foreclosure and short sales - rose 18 percent, from $107,500 in January to $127,000 in June, in Citrus, Hernando, Hillsborough, Pasco and Pinellas counties, according to Multiple Listing Service data.