Bonding between porcelain and Ni alloys containing 0 approximately 10 wt% Co and 0 approximately 25 wt% Cr is investigated. Experimental procedures are as follows. (a) Bonding strength between porcelain and alloys by pull out test (b) Expansion of alloys (c) Distribution of Ni, Co and Cr by EPMA (d) Macroscopic observation of fracture surface resulted by pull out test Following results were obtained 1) Pull out strength increased by addition of Co in all alloy systems. Pull out strength was lowest at 5 wt% Cr in Ni-Cr alloy system, at 15 wt% Cr in Ni-5 wt% Co-Cr alloy system, and at 20 wt% Cr in Ni-10 wt% Co-Cr alloy system. More addition of Cr increased the pull out strength. 2) The influence of alloying element on thermal expansion was not observed by addition of Cr and Co to Ni. 3) The thickness of the oxide film of alloys containing 5 wt% Cr was the largest, and it was remarkably decreased by more addition of Cr. 4) The fractography of porcelain showed a various patterns in relation to pull out strength. 5) At Ni-Cr-Co alloy surface oxide of porcelain side, Co concentration is slightly higher than Ni.