In the age of postinstitutional care, less attention is paid to the residual population of developmentally disabled persons within public facilities. Many such individuals are court ordered from the criminal justice system; they require varying intensities of mental health services. Level of risk to self and others is one component assessed by service providers as they plan resource allocation to meet the residents' support needs. Although it may be presumed that lower-functioning clients need more mental health services, this has not been tested systematically. The Developmental Disability Risk Inventory (DDRI) was designed to measure high-risk behavior in adults with developmental disability. This study investigated intellectual functioning, adaptive functioning, and high-risk behavior in 92 persons with mental retardation. The results indicated that DDRI scores correlated positively with level of intellectual functioning but did not show a statistically significant relationship with level of adaptive functioning. Together, these findings suggest construct validity for the DDRI. Implications for the clinical and forensic utility of the DDRI are discussed.