Multiple sclerosis (MS) is a disease of the central nervous system (CNS) that affects young adults. Survival is long, more than 35 years, and consequently the disease has a huge socioeconomic impact. The present article discusses the enormous difficulties of carrying out economic assessments in this field but also describes the advances made in research on this topic and the advantages of performing socioeconomic evaluations with increasingly sophisticated tools. We also discuss the need to quantify indirect and intangible costs to translate them into quality of life and subsequently into economic cost, expressed in euros in the case of Spain. The available data indicate that the enormous cost of the disease (1200 million euros per year) is due more to disability-related expenditure than to treatment, which-although expensive-does not represent more than 16-18% of the total expenditure (approximately 200 million euros per year). The increase represented by the cost of MS is not based on higher treatment expenditure but on an increase in the incidence and-especially-the prevalence of the disease. Above all, in the last few years, there has been a considerable rise in the percentage of patients with an indication for treatment. Reflection is therefore needed on the use of drug therapy in MS, since a saving in the most effective products seems to increase the overall cost of MS, while expenditure on these drugs represents a saving in the long-term.