The purpose of this quasi-experimental study was to examine the effect of an intervention for caregivers of individuals with Alzheimer's disease and related dementias (ADRD) on nursing home residents' functional and cognitive status. Fourteen special care units (SCUs) in 14 midwestern nursing homes were paired according to size, ownership, and staff turnover. The paired nursing homes were randomly assigned to either experimental or control groups. The intervention consisted of the Family Involvement in Care (FIC) protocol. The FIC intervention was designed to help family caregivers of nursing home residents with dementia negotiate and establish a partnership with the staff caregivers for the care of residents. One hundred sixty-four residents participated in the study, 71 in the control group and 93 in the experimental group. Sixty-three residents were lost to attrition (38%). The experimental group exhibited less global deterioration throughout the study. Inappropriate behavior, cognition, and functional status remained relatively unchanged over time within and between the groups. Increased family involvement did slow global deterioration in individuals with ADRD. The findings of the study show that more factors need to be examined to discover those interventions that preserve functional and cognitive abilities.