Although multiple sclerosis (MS) is often looked on as a disorder of the sensory and motor systems, it can also be associated with changes in emotion and personality. Many patients with MS seem cheerful, optimistic about the future, and strangely unconcerned about their ongoing physical deterioration. In addition, patients with MS have a tendency to break into uncontrollable laughing, even when they have no reason to be happy. This article looks at how these seemingly upbeat affective changes were viewed by early researchers of MS, including Cruveilhier, Charcot, and Moxon during the 19th century and Cottrell, Wilson, and Ombredane in the 1920s. Frequently cited studies on the emotional correlates of MS from the mid-20th century are also presented, and some trends in the more recent literature are identified.