Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS). It affects usually young people between 20 and 40 years of age, predominantly women. According to Lublin and Riengold classification there are four major clinical patterns of MS course: remitting-relapsing, primary progressive, secondary progressive and progressive-relapsing. Making definite diagnosis of MS is becoming recently very important because of development of some new immunomodulatory therapies of MS with proven effectiveness when used at the early stage of the disease. Because of the huge diversity of MS clinical signs and symptoms as well as the course of the disease, there are several other diseases with similar clinical picture. Differential diagnosis of MS includes such disease as: acute disseminated encephalomyelitis (ADEM), neuroboreliosis, neurosarcoidosis, systemic lupus erythematosus (SLE), Sjögren’s syndrome, CNS vasculitis, Behçet’s disease, antiphospholipid syndrome and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). Very important in MS differential diagnosis are some laboratory findings. The most useful techniques are magnetic resonance imaging (MRI), cerebrospinal fluid (CSF) examination, visual evoked potentials (VEP) and some blood tests. They often facilitate differential diagnosis of MS at the early stage of the disease. This is very important because the proper treatment can be initiated early.