BACKGROUND: There are few published health technology assessments that have included the impact of a disease or treatment on caregivers' health related quality of life (HRQL). The objectives of this study were to explore the overall HRQL of caregivers of people with multiple sclerosis compared to matched controls, and more specifically explore the impact of different levels of functioning in people with MS on caregivers' HRQL scores. METHODS: A cross sectional observational study conducted as an online survey was undertaken in the UK.