Objectives: The purpose of this study was to evaluate reasons for stopping interferon-beta therapy in patients with multiple sclerosis, to ascertain rate of patients stopping of their own will, and to identify associated factors. Patients and Methods: This cross-sectional study was conducted at Department of Neurology, Split University Hospital Centre. 85 patients with multiple sclerosis, treated with interferon-beta between 1996. and 2012., were included in the study. Application forms for interferon-beta therapy provided demographic and clinical data. Main outcome measures were therapy duration, disability progression represented as EDSS score increase, and occurence rates for specific discontinuation reasons. Results: There were 65 female and 20 male patients. There were 41 patients who stopped interferonbeta therapy, while 44 patients were receiving therapy at the time of assessment. Gender, age at therapy commencement and disease duration were not predictive of treatment discontinuation. Main reasons for treatment cessation were disease progression and own-will decision. Product type was not associated with discontinuation. Level of disability, represented as EDSS score, was found to be a significant predictor of treatment discontinuation. EDSS score at therapy commencement was significantly higher in the group of patients no longer receiving therapy (t(70)=3.3, p=0.001). Patients who stopped therapy also had significant increase of EDSS score between therapy commencement and cessation (t(26)=-2.4, p=0.02). There was also significant reduction of EDSS value between therapy commencement and last follow-up for patients who are still receiving interferon-beta therapy (t(35)=0.4, p=0.003). Conclusion: Study confirms that level of disability at treatment commencement, expressed as EDSS score, influences treatment duration. Lower EDSS value at treatment commencement was associated with greater treatment efficacy. Interferon-beta therapy for patients in inflammatory stages of multiple sclerosis delays disease progression and enables recovery of incurred disfunctions.