To estimate the socio-economic impact of multiple sclerosis (MS) in Italy. Outpatients with MS were enrolled at 44 centres across Italy. Socio-demographic, clinical and resource utilization data were collected using a validated questionnaire. Each patient completed a weekly diary of expenses due to MS over a three-month period. Direct health care costs and indirect costs (lack of productivity for the patient and for caregivers) were assessed for the whole population and were compared among five groups, categorised by disease severity (EDSS score). An analysis of variance was carried out on socio-demographic variables. For the total population of 566 patients, the mean direct cost over three months was ITL 2,134,000, the mean indirect cost was ITL 7,775,000. Costs were significantly higher for male patients (p < 0.05) and showed a significant increase with increasing age (p < 0.0005), disease duration (p < 0.0005) and disease severity (p < 0.0005). Costs for patients in a progressive phase were significantly higher (p < 0.0005). There were no significant geographical differences among the regions of Italy. This study confirms that MS represents a high economic burden, with indirect costs greatly exceeding direct costs. Unpaid caregivers remain the culturally accepted mode of care for MS patients in Italy and this study illustrates the impact of their loss of earnings. As costs increase with disease progression, these findings suggest that treatment efforts should focus on patients in the early stages of MS, in order to slow down disease progression.