The purpose of this study was to evaluate the effect of spure designs and air vent on the relative castability of the nonprecious alloys, commonly used to make ceamometal restorations. Samples of total 30 were constructed and devided into 6 groups according to two variables, sprue design and air bent. The total number of completly cast squares was counted, verified, and recorded. The results obtained were as follows: 1. The runner bar or Rousseau designs yield better castability than reservoir design(P<0.1) 2. When the air vent was attached, only the castability of reservoir design was significantly different from runner bar or Rousseau designs.