April's price movement was revised from a previously reported fall of 0.5 percent.
With the revision, import prices in May fell for the first time since October 2011.
With the price drop in May, import prices have fallen in four of the past 12 months. Over 12 months, import prices as of May were down 0.3 percent.
In the past 12 month, import prices for fuel are down 3.9 percent, a sharper drop than the 1.7 percent decline on a 12-month basis posted in April.
The change stands in sharp contrast to the 43.7 percent price gain for imported fuel from May 2010 to May 2011.
From April to May, prices for imported fuel fell 4.2 percent after dropping a revised 0.7 percent in the previous month.
For non-fuel imports, prices fell 0.1 percent April to May. For the 12 months prior, non-fuel import prices have risen 1 percent.
Export prices fell month-to-month, dropping 0.1 percent. Export prices for agricultural goods fell 1.3 percent, while prices for non-agricultural exports rose 0.1 percent.