1. Pink Disease is a new symptom-complex chiefly seen in babies of from three to eighteen months. Ten personally observed cases are recorded in detail. 2. The symptoms are characterised by - (a) a condition of extreme misery, insomnia, irritation, sweating and photophobia; (b) skin rashes with erythroedema of the hands and feet; (c) extreme muscular hypotonia. 3. The condition is probably of an infective nature, and may be due to a neurotropic virus akin to that of epidemic encephalitis. The mesencephalic centres of the sympathetic nervous system are affected, and changes also occur in the spinal cord and peripheral nerves. The cerebral cortex appears to escape involvement in the great majority of cases. 4. The mortality is by no means low, and has been placed as high as 30 per cent by some writers. Death is usually due to secondary infections, but may occur suddenly and unexpectedly. 5. The main necessity in treatment is skilled nursing.