Epidemic encephalitis made its appearance in Glasgow in 1918, although it was only in 1919 that its prevalence was such as to lead to its recognition. It recurred annually till 1924, and, during this period, the change in the clinical features from year to year suggested that it had passed through an evolutionary phase. While ocular symptoms were probably the features most common to all epidemics, prolonged lethargy and somnolence characterised the earlier cases; choreiform and myoclonic movements were more prevalent in 1920 and in 1921, while in 1924 there appeared for the first time a considerable proportion of cases with spinal signs and symptoms, which simulated acute attacks of insular sclerosis.