The majority of care of patients with Parkinson's disease (PD) is provided by informal caregivers; their caregiving not only offers physical and emotional support for patients but also plays a large economic role and prevents early nursing home placement. In order to support caregivers in this role, it is necessary to understand the extent of caregiver-burden and factors associated with increased caregiver-burden and distress. We therefore conducted a postal survey in 123 caregivers of patients with PD to assess caregiver-burden and factors associated with it. The majority of caregivers were female (66%). Over 40% of caregivers indicated that their health had suffered as a result of caregiving, almost half had increased depression scores, and two-thirds reported that their social life had suffered. After adjustment of disease duration, there was no difference in caregiver-burden between younger and older caregivers, or between male and female caregivers. Caregiver-burden increased with increasing disability and symptoms of PD, particularly with mental health problems such as depression, hallucinations, or confusion, and with falls. Caregiver-burden scores also correlated significantly with the patients' depression and quality of life scores, and with caregivers' own satisfaction with their marital and sexual relationship. We conclude that more attention should be paid to caregivers' emotional and physical health, particularly in advancing PD with psychiatric complications and falls. These findings also demonstrate that caregiver and patient quality of life are closely linked and emphasize the importance of including caregiver-burden among the problems associated with PD in order to improve patient and caregiver lives.