There are many types of chronic ulcerations of the skin observed in the tropics, and these may at times have very different etiologies. Such lesions may be associated with the presence of Treponema pallidum or T. pertenue. Sometimes they may be associated with Mycobacterium leprae (Bacillus leprae) or Leishmania tropica. In some instances, ulcerations may develop as a result of infections with ordinary pyogenic organisms in the skin of individuals whose resistance has been lowered by such diseases as malaria, dysentery, or ancylostomiasis. Similar tibial ulcers have also been observed in patients with hookworm disease. There is, however, a very common form of ulceration known as tropical sloughing phagedena or tropical ulcer, which many consider as a clinical entity, and the most striking feature of these lesions is the presence of spirochetes and fusiform bacilli in the lesions. These organisms not only are found on the surface of