The lead isotopic ratios of a carefully selected suite of ore samples from the Laurion region were determined by a precise mass spectrometricprocedure. The ores were taken from various levels in mines, some known to have been worked in ancient times. All are nearly indistinguishable isotopically within the precision of the method (+0.05%), and they closely match leads from archaeological objects found in Greece. A comparison with isotopic data for ores from other mining regions in the ancient world has been made. The uniformity of the Laurion ores facilitates the interpretation of lead isotope data for archaeological objects from Greece.