Multiple sclerosis (MS) is an acquired chronic immune-mediated inflammatory condition of the central nervous system (CNS), affecting both the brain and spinal cord. It affects approximately 100,000 people in the UK. It is the commonest cause of serious physical disability in adults of working age. People with MS typically develop symptoms in their late 20s, experiencing visual and sensory disturbances, limb weakness, gait problems, and bladder and bowel symptoms. They may initially have partial recovery, but over time develop progressive disability. The most common pattern of disease is relapsing–remitting MS (RRMS) where periods of stability (remission) are followed by episodes when there are exacerbations of symptoms (relapses). About 85 out of 100 people with MS have RRMS at onset. Around two-thirds of people who start with RRMS may develop secondary progressive MS: this occurs when relapses are initially associated with progressively less complete recovery, then subsequently individuals gradually develop worsening symptoms without any clear remissions. Also about 10 to 15 out of 100 people with MS have primary progressive MS where symptoms gradually develop and worsen over time from the start, without ever experiencing relapses and remissions. The cause of MS is unknown. It is believed that an abnormal immune response to environmental triggers in people who are genetically predisposed, results in immune-mediated acute, and then chronic inflammation. The initial phase of inflammation is followed by a phase of progressive degeneration of the affected cells in the nervous system. MS is a potentially highly disabling disorder with considerable personal, social and economic consequences. People with MS live for many years after diagnosis with significant impact on their ability to work, as well as an adverse and often highly debilitating effect on their quality of life and that of their families. This guideline replaces NICE clinical guideline 8 (2003) and covers diagnosis, information and support, treatment of relapse and management of MS-related symptoms. The guideline does not address all symptoms and problems associated with MS. Some areas are addressed in other NICE guidance for example urinary symptoms and swallowing, and these are referenced where appropriate. Many of the interventions used in a rehabilitation setting to alleviate symptoms such as tremor, weakness, cardiorespiratory fitness, sensory loss, visual problems (apart from oscillopsia), and secondary complications of immobility such as deconditioning and contractures have not been covered because these are beyond the scope of the guideline. Many of these problems are complex and need individual assessment and management strategies. These assessments and treatments need to be carried out by healthcare professionals with appropriate expertise in rehabilitation and MS. The guideline does not address the use of disease-modifying treatments; there are NICE technology appraisals about these treatments. The guideline is aimed primarily at services provided in primary and secondary care. It does not map out a model of service delivery. Many people with MS may also attend specialised tertiary services, often established particularly to provide and monitor disease-modifying therapies.