Publisher Summary This chapter describes clinical features and subtypes of multiple sclerosis (MS). MS is a disorder of the immune system with an impact on the central nervous system (CNS) and thus can produce any constellation of symptoms and signs that might occur from a lesion or lesions in areas of the brain, spinal cord, and optic nerves. Symptoms and signs in MS reflect primarily—but not exclusively—white-matter involvement, although the body of data implicating neuronal injury is growing. Variability of signs and symptoms—in type and in timing—is a hallmark of MS. A constellation of clinical problems, some more frequently seen than others, occur in the disease, generally different in different individuals and different over time in the same individual. Although specific signs and symptoms may not be attributable to specific pathological conditions, the clinical features of MS are best understood in the context of the knowledge of the neurophysiological and neuropathological consequences of inflammatory, primarily demyelinating, disease.