Objective: Caregivers of patients with advanced cancer experience physical and emotional strain that can raise their own risk for morbidity and mortality. This analysis was performed to determine whether ENABLE II, a patient-focused palliative care intervention that increased patients' quality of life, reduced symptom intensity, and lowered depressed mood compared to usual care, would affect caregiver burden. Method: Caregivers of patients with advanced cancer from the parent study completed a caregiver burden scale and patients completed quality of life, symptom intensity, and depressed mood measures. Data were collected at baseline, 1 month, and every 3 months thereafter until patient death or the study ended. Decedents' caregivers were asked to complete an after-death interview regarding the quality of care that the patient received. Results: There were no significant differences in caregiver burden between intervention and usual care conditions. Follow-up analyses showed that higher caregiver objective burden and stress burden were related to lower patient quality of life, higher symptom intensity, and higher depressed mood. Caregivers who perceived that patients had unmet needs at end of life reported higher objective burden, and those who perceived that patients were not treated with respect reported higher demand burden. Significance of results: The results indicate that a successful patient-focused intervention did not have a similar beneficial effect on caregiver burden. Future interventions should focus on caregivers as well as patients, with particular attention to caregivers' perceptions of patient care, and seek to change both negative and positive effects of informal caregiving. Copyright © Cambridge University Press 2010.