A malignant tumor of the second metatarsal in a thirteen-year-old girl with trouble-some clinical and especially light- and electronmicroscopical aspects is described. The findings are discussed in relation to each of the two possibilities to be considered: highly malignant, extra-cranial so-called adamantinoma (poorly differentiated or basaloid type) or Ewing's sarcoma with focal squamous differentiation, the latter being a most remarkable observation.