Despite the advances of medicine, many illnesses continue to evade cure. Chronic, progressive, incurable illness is a major cause of disability, distress, suffering, and, ultimately, death. This is true for many causes of cancer, AIDS, and other disorders of vital organs. Such progressive, chronic diseases are most common in late adulthood and old age, but they occur at all ages. Disease-modifying treatments and the relief of suffering through symptom management, care planning, and family support are central to care, and these four domains are core goals of palliative care. This chapter offers an overview of how epidemiological studies may be used to clarify the population/s of people who may benefit from palliative care, to assist the planning for how services may meet the needs of people towards the end of life. Symptoms associated with a series of common, progressive, chronic illnesses will be discussed, thereby further facilitating planning for individual patients and for services.