Background: The aim of this study was to reevaluate the reliability (internal consistency, inter-rater and re-test) and the factor structure of the Behavior Problems Inventory (BPI-01) with adults with intellectual disabilities who resided in a state-run developmental centre. Methods: BPI-01 was administered to informants who had known participants for a minimum of 6 months. For study 1, data were collected in two samples: 100 residents who were selected based on the challenging behaviour targeted in their behaviour treatment plan and 325 randomly selected residents. Results: The internal consistencies of the BPI-01 subscales were in the good to excellent range. Overall, the inter-rater and test-re-test reliability of the subscales and items were adequate with relatively lower reliability found for the Stereotypy subscale and items. For study 2, the data of the 425 participants from study 1 were used in a confirmatory factor analysis, which indicated that three a priori BPI-01 subscales (Self-Injurious Behavior, Stereotyped Behavior and Aggression/Destruction) were a reasonable fit. Conclusions: The current study provides additional support to the reliability and factor structure of the BPI-01 in adults with intellectual disabilities.