Background: In a previous study, we had evaluated short-term effects of interferon beta-1a (IFNB-1a) 44 mu g s.c. three times per week treatment on serum levels of IFN-gamma (IFNG), IL-23, IL-17, IL-10, IL-9, IL-4 and TGF-beta (TGFB) and found a reduction only in IL-17 and IL-23 levels after 2 months of treatment. Methods: Using the same multiple sclerosis (MS) cohort, we assessed the predictive value of early cytokine level changes (difference between 2nd month and baseline levels as measured by ELISA) on the efficacy of long-term IFNB-1a treatment. Results: The alteration in IFNG levels of patients without any relapse was statistically lower than that of patients having one or more relapses (p = 0.019, Student's t-test). When patients with or without expanded disability severity scale (EDSS) progression were compared, none of the cytokine level changes showed a significant difference between groups. IL-17 and IL-23 level changes did not predict relapse and EDSS progression in IFNB-1a-treated MS patients. Conclusion: Our results show that the predictive power of early IFNG measurement on relapse occurrence may potentially extend a time span of several years.