While infestation with the body louse (Pediculus humanus) is not infrequent in our civilian population, it does not constitute a serious public health problem. Under wartime conditions, however, when large numbers of our combat forces may become infested with this parasite, there is the possibility of their developing the various diseases for which the lice are vectors. In addition many observers believe that the discomfort from the accompanying pruritus may reduce the efficiency of the infested men. The timely importance of the problem seemed to warrant additional work on the dermatologic phases of louse infestations. The maintenance of a large colony of lice for use in insecticidal investigations in the Division of Zoology afforded an opportunity for observing cutaneous lesions and for conducting intradermal and other tests on persons who had fed lice over relatively long periods of time. REVIEW OF THE LITERATURE According to most authors, the earliest manifestations