Patients with incurable illness experience considerable physical and psychological distress, which negatively impacts their quality of life. Palliative care clinicians primarily seek to alleviate suffering, enhance coping with symptoms, and enable informed decision making. In this article, we review the efficacy of various palliative care interventions to improve patients' quality of life, physical and psychological symptoms, satisfaction with care, family caregiver outcomes, health-service utilization, and quality of end-of-life care. We have identified 22 randomized studies that evaluate the efficacy of various palliative care interventions. Palliative care research has been hampered by methodological challenges related to attrition and missing data due to progressive illness and death. In addition, interventions to date have varied widely in the focus and extent of services, with only eight studies entailing direct clinical care by palliative care specialists, making comparisons across trials challenging. Despite these limitations, accumulating evidence shows that palliative care interventions do improve patients' quality of life, satisfaction with care, and end-of-life outcomes. Five of seven studies which examined quality of life as a primary outcome reported a statistically significant difference favoring the palliative care intervention. Ten studies examined patient and/or family caregiver satisfaction with care, and seven of these reported greater satisfaction with palliative care intervention. However, data are lacking to support the benefit of palliative interventions for reducing patients' physical and psychological symptoms. We conclude the review by discussing the major obstacles and future directions in evaluating and implementing standardized palliative care interventions.