The question of what kind of drills were used to produce the holes in 24 stone cylinder seals from ancient Mesopotamia was attacked by making experimental drillings in modern materials and comparing the markings in the holes with those in original artifacts. Comparison was done from silicone rubber replicas studied in the scanning electron microscope. 12 seals in marble or calcite from ca. 3100 to 2900 BC had holes identical to those produced in marble by a drill of chipped flint. 12 seals in hematite (11) or limonite (1) from 2000 to 1600 BC had holes identical to those produced in hematite by a copper rod drill with a slurry of emery grit in oil or water. -- AATA