Impairment of respiratory function has been described in end-stage multiple sclerosis (MS), as well as in patients with mild to severe disability. No data are available regarding the respiratory function of MS patients without disability. The objective of this study was to assess the pulmonary function, respiratory muscle strength and carbon monoxide diffusion capacity of the lungs (DL(CO)) in patients with relapsing-remitting multiple sclerosis (RRMS) without disability.