The peroxisome proliferator-activated receptor gamma agonist pioglitazone is FDA-approved for treatment of type-2 diabetes due to insulin sensitizing effects. However pioglitazone has anti-inflammatory and neuroprotective effects, reduces glial and T-cell activation, and reduces signs in an animal model of multiple sclerosis (MS). We tested the effects of daily treatment with pioglitazone in a small cohort of relapsing remitting MS patients. RRMS patients taking IFNbeta-1alpha and having an EDSS score <6.5 were randomized to treatment with pioglitazone (30 mg daily, p.o.) or placebo and monitored clinically and by MRI for 1 year. Primary outcomes were safety and tolerability, secondary outcomes included changes in neurological outcome, lesion burden, and gray matter volume. After 1 year 11 patients in the pioglitazone arm and 10 in the placebo arm completed the trial. Pioglitazone was well tolerated with a similar incidence of non-serious adverse events in placebo and treatment groups. After 1 year there were no significant differences in clinical symptoms as assessed by EDSS; however MRI showed a significant reduction in gray matter atrophy, and a trend for reduced lesion burden in the treatment group. These results show that pioglitazone was well tolerated in RRMS patients with indications of beneficial effects, warranting further trials to establish clinical efficacy.