Every day, in households across the country, people engage in behavior to improve their current health states, recover from disease and injury, or cope with chronic, debilitating conditions. Innovative computer and information systems may help these people manage health concerns, monitor important indicators of their health, and communicate with their formal and informal caregivers. Designers and developers can help change the face of health care at home by creating appropriate consumer health information technology (IT) applications. This guide introduces designers and developers to the practical realities and complexities of managing health at home. It provides guidance and human factors design considerations that will help designers and developers create consumer health IT applications that are useful resources to achieve better health.