There are a number of illnesses that can mimic multiple sclerosis (MS). This pretty much includes any pathological process that can reflect injury to the central nervous system either in a transient or progressive basis. Typically, MS presents itself in individuals in their teens up to their late 30s. On occasion, however, one can see MS present in patients in their 60s. However, in retrospect, many of these patients might have had subtle manifestations of MS in their younger years. Visual obscuration or visual loss can be a manifestation of retinal ischemia, retinal migraine, or optic neuritis which might or might not evolve into a clinical picture compatible with MS. Cranial neuropathy, long tract signs, sensory disturbance, and/or gait ataxia can be related to a number of different processes such as illicit drug use, neurosarcoidosis, neuro-Behcet's disease, neuroborreliosis, HIV-related disease, neurosyphilis, vascular occlusive disease including vasculitis, connective tissue disorders, acute disseminated encephalomyelitis (ADEM), idiopathic transverse myelitis, neuromyelitis optica (NMO), or tropical spastic paraparesis. In addition, a constellation of symptoms, with questionable objective findings, along with normal MRI imaging, normal CSF results, and normal evoked response testing, when indicated, might identify a conversion disorder or possibly malingering. There are now established criteria for the diagnosis of MS, but initial presentations can be less than "textbook" in nature. With the advent of immunomodulating therapy, it has become more important to diagnose MS more effectively earlier on in the course of the illness. Prior to specific therapy for MS, astute clinicians did not necessarily move with alacrity to establish the diagnosis in patients with subtle or transient manifestations. This was in recognition of the fact that little could be offered to alter the course of the illness and a number of patients might never experience further problems if they were lucky enough to have their illness go into permanent remission after one minor exacerbation.