Methods: We restrospectively revised patients with MMN diagnosed in our EMG laboratory during last 15 years with a follow-up higher than 5 years and analyze clinical and electrophysiological findings in 3 stages of the disease evolution. We quantified the number and sites of definite conduction blocks (CB), probable CB, anomalous temporal dispersion (ATD), and axonal degeneration (AD). We established the diagnosis of definite MMN, probable MMN and MADSAM according to AANEM criteria at the moment of diagnosis, after 2 years and 5 or more years of monitoring. Results: We found 11 patients (7 male:4 female, mean age of 43 years) with MMN followed between 5 and 11 years. A significant decrease of definite and probable CB and increase of nerves with AD has been found. Sensory involvement appeared in 3 patients, one of them with worst clinical and electrophysiological evolution. Five patients changed the diagnosis during the follow-up. Conclusions: In the follow-up of patients with MMN during more than 5 years there are changes in the pathophysiology of nerve injury (definite and probable CB, ATD and AD), in sensory involvement and diagnosis according to criteria of AANEM. This fact complicates the diagnosis and monitoring of this disease.