Bromocriptine suppresses the duration and severity of clinical signs of experimental allergic encephalitis, which is considered as an animal model for multiple sclerosis (MS). We conducted an open pilot study with 2.5 mg of bromocriptine two times a day on 18 patients with clinically or laboratory-supported definite MS (10 with the relapsing-remitting form and eight with the chronic progressive form). After 1 year of treatment, 14 of the 15 patients who completed the study showed disease progression as evidenced by one or more of the following parameters: worsening of the EDSS score, clinical relapses, appearance of new lesions on MRI of the brain and brainstem, or increased latencies of visual or auditory evoked responses. These findings indicate that bromocriptine does not completely suppresses ongoing disease activity in patients with multiple sclerosis.