Examination of a set of pre-Columbian bronze tools made and used at Machu Picchu (Peru) shows that they were cast to nearly final form, that alloy content and degree of work hardening were apparently chosen to optimize tool performance, that iron and sulfur are the principal impurities present in the bronze, and that the copper used was probably smelted from sulfide ores. Most of the edge tools have been hammered upon in use and many have broken with nearly brittle fractures. The poor strength and ductility of the tools is due to sulfide inclusions and porosity. It is suggested that the metallurgical skills acquired in making decorative objects were not adequate to permit the Inca artificers at Machu Picchu to realize the full potential of the use of bronze for tools intended for heavy work.