The current study used an item response theory (IRT) framework to examine the psychometric properties of the long and short forms of the Behavior Problems Inventory (BPI-01 and BPI-S respectively). The BPI measures self-injurious, aggressive/destructive, and stereotyped behaviors as manifested among individuals with intellectual and developmental disabilities. With a sample of 1,122 individuals with intellectual and developmental disabilities, it is the first IRT examination of either form of the BPI. Results reveal acceptable psychometric properties for each form of the BPI as well as minimal differential item functioning according to sex.