This study compared the shear bond strengths and the prosity at the bond sites of a spherical amalgam alloy to those of an admised amalgam alloy, when they were bonded to like and unlike alloy specimens with or without a resin bonding material. The spherical alloy had higher bond strength and less porosity than did the admixed alloy, whether bonded to spherical or admised alloy. The results suggest that use of a spherical alloy should be strongly considered when an amalgam restoration is to be repaired with an amalgam alloy, regardless of the type of alloy used in the original restoration. Use of a resin bonding agent did not increase bond strengths of amalgam to amalgam.