1. Symptomatic herpes occurred in 190 (46.2 per cent) of 411 patients treated with fever induced by physical methods.
2. Herpes recurred in only 7, or 5.3 per cent, of 131 patients given subsequent fever treatments, suggesting that some immunity develops with the first attack.
3. An acute encephalitis-like syndrome of short duration and without sequelae developed in a group of patients with severe herpes following fever therapy.
4. A filter-passing virus, recovered from herpetic vesicles on patients treated with artificially induced fever, produced a fatal encephalitis in rabbits when inoculated intracerebrally and by corneal scarification. Intranuclear inclusion bodies were observed in corneal epithelial cells and in motor ganglion cells of the brain similar to those observed in rabbits injected with known strains of herpes virus.
5. Four strains of virus that had been recovered from herpetic vesicles appearing on patients subsequent to artificially induced fever were shown by cross-protection tests on rabbits to be immunologically related to the Frank strain of herpes virus.