Although much efforts have been paid to improve the properties of silver-tin amalgam, some clinical problems are not resolved yet. Palladium alloys have good properties for dental material, and they react on mercury well. So they are considered to be good amalgam alloys. In this paper, palladium base ternary alloys are studied for dental amalgam. The effect of size and shape of particle on dimensional change, compressive strength and hardness is studied. Main results obtained are as follows. (1) The dimensional change of spherical particle amalgam is smaller than that of fine cut particle. The finer the particle size is, the smaller the dimensional change is both for spherical and fine cut particles. (2) The dimensional change of amalgam of 60 wt% Pd-40 wt% Ag alloy decreased by addition of Sn or Cu, and these values under 20 micrometer/cm by addition of more than 5 wt% Cu or 10 wt% Sn. (3) Compressive strength of Pd alloy amalgam scatter so widely that the effects of alloying element are not able to be evaluated. Both maximum compressive strengths are 22 kg/mm2 and 28 kg/mm2 for the alloys containing Cu and Sn respectively. (4) Vicker's hardness of palladium alloy amalgam increased by addition of Sn and ranged 80 approximately 120 for spherical amalgam, which is higher than that of commercial alloy. Significant difference is not found in Cu added alloys. (5) From the analysis by XMA, it is found that matrix is composed of one phase and there is compositional difference between center of matrix and near the particle. Silver is rich in the center of matrix and palladium is rich near the alloy particle. Cu and Sn are seemed to distribute uniformly.