This study examined the incidence and nature of abuse of individuals with developmental disabilities residing with their families in New York State. Informal meetings were held with service providers to discuss the issues, and 84 allegations of familial abuse and neglect were reviewed. The study found that familial abuse of these individuals constitutes about 9% of all reports of alleged abuse and neglect filed by state-operated and state-certified residential and day programs serving persons with developmental disabilities. The most typical alleged victim was a young woman under 35 who was attending a day program and living at home. The alleged perpetrators were more likely to be male, and most were identified as a parent or other quasi-parental figure. Of the service providers that responded to a survey concerning their role in 1 or more of the 84 cases, over half indicated that they were less than fully satisfied with their ability to investigate the allegations. Approximately one-fourth of the reporting programs contacted law enforcement officials for help, while 66% contacted the local Adult Protective Services for help. Only 22% of those requesting adult protective services assistance were totally satisfied with help received. There was a higher likelihood of physical injury to the alleged victims in the familial reports, and victims were likely to be involved in multiple reports of abuse. Recommendations are presented which would clarify the responsibility for conducting investigations into allegations of familial abuse; develop close cooperative relationships between local social service districts and developmental disabilities service offices; reaffirm the reporting responsibilities of provider agencies; ensure the availability of emergency respite and short-term residential options; and provide primary prevention services including parent training. An appendix presents responses to the report from two New York government agencies. (JDD)