Mainly progressive multiple sclerosis (MPMS) is an uncommon clinical form of multiple sclerosis which includes 10 20% of all patients with the disorder. MPMS shows certain clinical characteristics which differentiate it from other forms of progression of the disease. We review the immunological and radiological behaviour of this clinical form, and discuss recent classifications of the disease and new diagnostic criteria. Finally we comment on the few therapeutic options currently available for these patients and their future prospects.