Multiple sclerosis (MS) is a demyelinating disease with damage of central nervous system, dissemination in time and space. Current McDonald’s MS diagnostic criteria are based on complex clinical and laboratory analysis (magnetic resonance imaging, MRI, evoked potentials, and cerebrospinal fluid analysis). Each of these laboratory tests supply different but very important information concerning type and range of central system damage. In MRI, special location and contrast enhancement of MS lesions are very characteristic for multiple sclerosis. Current MRI diagnostic criteria (Barkhof’s criteria) can be used to established evidence of dissemination in space. In dissemination in time, occurrence of a new lesion on T2-weighetd images or contrast enhancement on successive MRI exam is required. Magnetic resonance imaging plays also an important role in monitoring the MS therapy. Evoked potentials investigate visual, auditory, sensory and motor nerve tracts. They can detect clinically silent lesions and provide evidence for dissemination in space. In cerebrospinal fluid analysis the most important for MS diagnosis are the presence of oligoclonal bands and increase of IgG index. Often, more specific markers of the immunologic system damage are also explored. However, in MS, laboratory tests are very important and useful, the diagnosis of MS is still based mainly on clinical observation.