An interesting feature of the descriptions of the Plasmodium vivax infections acquired by military personnel in highly endemic areas in the south or southwest Pacific, is the frequency and number of the periods of clinical reactivation which some of these patients present, the episodes often continuing for some months after repatriation. Many are reported to have experienced 15 or more such episodes. The remissions setting these off were usually induced by the early initiation of conventional therapy, and have commonly been of rather short duration. Most would probably fall in the category of recrudescences rather than relapses as recently distinguished (Boyd and Kitchen, 1944). In the study cited, it will be noted that the number of such secondary episodes or attacks coming to our attention in the naturally induced vivax infections at the Florida State Hospital, never were observed to exceed six. The patients comprising this series had been inoculated only once with this species of parasite.