Until 2011, according to the FBI crime reporting guidelines, men cannot be victims of rape.

The FBI definition of forcible rape is set in page 19 in the UCR Guideline: The carnal knowledge of a female forcibly and against her will, which means men do not fall under this category. 

(Source)

Update: On Oct. 20th 2011, the FBI voted to change the definition to be more inclusive. Read it here