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The relation between the casting structure and sliding wear properties of lead and tin as the major components of leadbronze was investigated. The test pieces were cut out from the chilled, columnar and equi-axial structures of lead-bronze ingots of different composition and were slid on a hardened steel ring in air without any lubricant.The results obtained are as follows:(1) The equi-axial crystal part in the casting structure shows the best wear resistance properties, followed by the columnar crystal, and the chilled crystal is the worst generally. These trends are remarkable in the high lead and high tin alloy.(2) The worn surfaces of the chilled structure are always metallic and the wear phenomenon is severe. The surfaces of columnar crystals are metallic or oxidized. The degree of oxidation depends on the compositions and sliding conditions, and is not satisfactory as compared with the equi-axial crystals. The surfaces of the equi-axial crystals are easily oxidized and the amount of wear is very small, while the wear of the steel ring is often severe.(3) It is considered that the wear of lead-bronze is influenced by the distribution and shape of lead and the contents of lead and tin. The size of lead in the equi-axial crystal structure is relatively large and its distribution is relatively continuous each other.This form of lead is more preferable for wear resistance than the fine and isolated form of lead in the chilled structure.(4) The materials with stable oxidizing wear seize the mating steel and show a high coefficient of friction, and these phenomena are relaxed by a suitable addition of lead.