Interferon-beta (IFN-beta) is an effective treatment for a subgroup of patients with multiple sclerosis (MS). The mechanism of action as well as the pathophysiological basis of responsiveness to IFN-beta is not well understood. To improve treatment considerations in MS patients predictive markers for response to IFN-beta therapy at early timepoints are needed. Here we correlated changes in serum cytokine levels (IL-13, IL-10, IL-5, IL-4, IFN-gamma) with the clinical response to IFN-beta treatment. Serum cytokine levels of 77 untreated and 43 IFN-beta treated relapsing-remitting MS patients (RRMS) were measured by ELISA, including longitudinal measurements in 17 patients. We found a significant upregulation of IL-10 and IL-5 serum cytokine levels during IFN-beta therapy. However, clinical response was only associated with IL-10 serum levels (p=0.038; positive predictive value 0.95, negative predictive value 0.43) but not with IL-5. The predictive power was increased by a combined testing of IL-10 with expression of co-signaling molecules on monocytes, that were previously shown to change during IFN-beta therapy. In a subgroup of 17 patients testing of 4 markers had a positive and negative predictive value of 1.0 for at least 2 of these markers being positive in treatment responders. The results suggest that serum IL-10 is useful to predict treatment response to IFN-beta particularly in combination with a panel of other IFN-beta dependent parameters.