The effects of the opaque porcelain firing temperature, the bonding agent and the degassing prior to the opaque firing On the bond strength were investigated by means of the tensile shear stIe$. The diffusional behaviours at the interface of the porcelain and the alloy, and .the microstructures of the ceramic and metal composite were studied for understanding the bonding mechanism. The results obtained in this experiment were summarizd as follow; 1. With no application of bonding agent, the tensile shear strength of the specimen firing at $1840^{circ}F$ was higher than that of the specimen firing at $1760^{circ}F$. 2. The highest bond strength was obtained by application of bonding agent without degassing prior to the opaque firing. 3. Application of bonding agent after the degassing showed the lowest bond strength. 4. The greater number of pores were observed at the firing temperature of $1840^{circ}F$ than that of $1760^{circ}F$ in the porcelain and the interface respectively.