BACKGROUND Charcot-Marie-Tooth disease (CMT) type 2 is the axonal variant of an inherited, sensorimotor polyneuropathy. To our knowledge, the clinical course of CMT type 2 has never been prospectively studied in a large group of patients. OBJECTIVE To prospectively evaluate the disease course of patients with CMT type 2. METHODS We prospectively evaluated the disease course in patients with CMT type 2. Forty-three patients (24 men) of 27 families with CMT type 2 were included. All patients were analyzed by the same investigator at entry and after 5 years. The standardized protocol included manual muscle testing, which could lead to a motor sum score of 140 points, and quantification of sensory deficit. Disability was assessed using the modified Rankin scale, and quality of life was assessed using the RAND 36-item health survey questionnaire. Eighteen families were tested for known mutations in the MPZ, PMP22, and GJB1 genes. RESULTS At entry, the mean +/- SD age of the patients was 52 +/- 14 years, and the mean +/- SD duration of disease was 12 +/- 8 years. The median motor sum score deteriorated from 135 to 128 points (P =.02). Progression was never rapid. There was no sensory deterioration. The Rankin score decreased by 1 point in 16 patients. At follow-up, more patients needed walking aids, but most patients remained ambulant. The number of patients with claw toes increased, whereas the number of patients with foot deformities such as pes cavus and short calf muscles remained stable. There was no correlation between deterioration and age. Analysis of quality of life did not show any changes. In one family, a mutation in the GJB1 gene was found. CONCLUSIONS This prospective study shows a slow deterioration of muscle strength and increase in disability in CMT type 2 during a 5-year follow-up period.