Several 16th century cannon balls were analyzed and shown to contain large amounts of Fe, Zn, Ba, and S (27, 15, 11, and 10% respectively). These cannon balls were prepared from slags of Pb smelters, and the unusually high content of Ba was naturally and unintentionally introduced from Ba-rich smelter slags. The principal phases within the cannon ball were recognized by light microscopy, microprobe analysis and x-ray diffraction analysis as Zn sulfides, Fe oxides, and spinels and silicates of Ba, Ca, Mg, and Al. The poor healing of wounds produced by these cannon balls may have been due to toxic effects of the Ba, Zn, and S. -- AATA