During the first 18 months after establishment of the Behaviour Assessment and Intervention Service (BAsIS), 31 clients living in Sydney Residential Aged Care Facilities were referred. Following comprehensive assessment, the BAsIS team recommended primarily psychosocial and environmental interventions that were case-specific and causality-focused. Behavioral observations and standardized measures of mood, behavior, and carer stress in relation to caring for the resident were collected at initial assessment, and at 6 to 8 weeks after implementation of the BAsIS program. Twenty-two residents completed BAsIS programs. Following BAsIS interventions, there was a significant improvement in resident mood and a significant reduction in carer stress. The results support the feasibility of a case-specific, causalityfocused approach in addressing challenging behaviors in longterm care, and suggest that improved mood for nursing home residents and reduced carer stress can be achieved with relative cost effectiveness.