The purpose of this study was to evaluate the quality of life (QoL) of multiple sclerosis (MS) caregivers, and to determine relationships that may exist between caregiver and patient QoL. Patients with definite MS (n=445) and their caregivers (n=445) were required to complete the generic, 36-item short-form (SF-36) Health Survey. Median SF-36 dimension scores ranged from 55 to 100 for caregivers and from 46 to 78 for patients. Although the QoL of MS carers was not as severely affected as that of patients, caregiving was associated with lower mental health, vitality and general health scores, compared to healthy subjects. Multivariate analyses revealed significant differences between the predictors of patient QoL and caregiver QoL. The main predictors of patient QoL were Expanded Disability Status Scale (EDSS) score, MS course, fatigue and depression. Female gender and advanced age were the main predictors of lower QoL in caregivers. In addition, patient BDI score was found to be a significant predictor of almost all caregiver SF-36 dimension scores, while EDSS score, disease duration and course, and patient therapeutic characteristics were found to be predictors of some caregiver SF-36 dimension scores. Therefore, caregiver QoL was significantly influenced by patient characteristics, and supportive strategies for MS caregivers are warranted.