The current U.S. health care system is not structured to adequately meet the needs of the growing number of people with chronic conditions. In 2004, almost half of all Americans, or 133 million people, live with a chronic condition. That number is projected to reach 157 million by 2010. People with chronic conditions account for 83 percent of health care spending and those with five or more chronic conditions have an average of almost fifteen physician visits and fill over 50 prescriptions in a year. This chartbook provides an overview of chronic health conditions in the United States and the impact of these conditions on individuals, their caregivers and the U.S. health care system. It outlines demographic information, prevalence rates and projections for people with chronic conditions, and details spending and utilization for people with multiple chronic conditions and activity limitations. Data sources for the chartbook include the 2001 Medical Expenditure Panel Survey (MEPS), the 2001 Medicare Standard Analytic File, three commissioned opinion surveys, and the 1996 Survey of Income and Program Participation (SIPP). The data presented suggest that care provided in the current acute, episodic model is not cost-effective and can lead to poor outcomes. In order to make clinical treatment more effective, services need to be more readily available and coordinated with emphasis on early diagnosis and interventions that maintain health status and minimize episodes of acute illness. This chartbook, an update of the 2002 "Chronic Conditions: Making the Case for Ongoing Care," was prepared by Partnership for Solutions, a national program funded by the Robert Wood Johnson Foundation and based at Johns Hopkins University. One important limitation of the data analysis is that it does not always capture information on people whose chronic condition is a disability or functional limitation without an underlying chronic illness.