OBJECTIVES: To determine patients' views on the impact of multiple sclerosis (MS) in terms of symptoms experienced, impact on day-to-day functioning and overall quality of life (QoL). METHODS: In-depth, unstructured qualitative interviews were conducted with MS patients recruited via the MS Society in the UK. Thematic analysis was conducted on interview transcripts to identify key impact areas. Interpretive phenomenological analysis (IPA) was conducted to explore and interpret participants' perceptions of impact; specifically, the meaning and importance patients ascribed to areas of impact. RESULTS: Interviews were conducted with 35 individuals (15 males / 20 females). Patients were aged 31-75 (mean 50; SD 13.2) years with MS duration of 2-58 (mean 17.7; SD 14.2) years. Eleven (31.4%) had relapsing-remitting MS, 10 (28.6%) had secondary-progressive, two (5.7%) primary-progressive, two (5.7%) benign MS and one (2.9%) progressive-relapsing. MS-type was unknown by nine (25.7%) individuals. Key areas of symptomatic impact reported were fatigue, pain, incontinence and mood fluctuation. Impact on memory and broader cognitive problems were less commonly reported. Key areas of functional impact related to physical incapacity (difficulty/inability walking, difficulty using stairs), problems conducting/completing activities of daily living, personal care, impact on social functioning, sexual functioning and work life. IPA analysis revealed that the most profound effects of symptomatic and functional problems were experienced in relation to impact on quality of intimate and social relationships, self-esteem, loss of identity, personal development/fulfillment and fear of the future. CONCLUSION: The interviews provided a rich source of information about the nature of the impact of MS and the concerns of affected individuals. These data will be used to generate content for new MS-specific patient reported outcome scales of symptoms, functioning and quality of life (QoL) suitable for use in clinical trials.