The impact of a disease on a patient has become an important outcome measure in medicine and health care. More recently, increasing attention has also been paid to the impact on informal caregivers of someone with a long-term disease. Carers or caregivers play an important role in the care of chronically ill patients, particularly because there is an increase in the number of people with a long-term condition. Vitaliano et al. define informal carers as “caregivers who are not financially compensated for their services.” Informal carers tend to be family members, often the patient’s spouse, or friends, and provide significant amounts of support to the patient who may have difficulties because of physical, cognitive, or emotional impairments. Caring for someone with ill health poses challenges, including psychological, physical, financial, and social factors. It is increasingly recognized that caring for someone can be stressful and difficult and that it can lead to adverse physical and psychological outcomes for the carer. Two types of outcome measures have been used to assess carer burden: generic and carer-specific outcome measures. Using generic instruments is an indirect approach to assessing carer outcomes, whereas using a carer-specific instrument is a direct approach to the assessment of carer outcomes. Generic instruments provide broad insight into health, but they do not provide information on the burden resulting from being a carer. Generic outcome measures tend to have been tested extensively, but mostly not in a carer population. © Cambridge University Press 2011