This study investigated the effect of poweder/water ratios of irreversible hydrocolloid on the tensile bond strength of several irreversible hydrocolloid and agar combinations. Each irreversible hydrocolloid was prepared in three different powder/water ratios as follows: (1) normal recommended ratio, (2) 10% more water than normally recommended, and (3) 10% less water than normally recommended. The irreversible hydrocolloid and the agar were joined together in a special loading assembly, which was subjected to tensile loading. The results suggest that except for one irreversible hydrocolloid and agar combination the powder/water ratio had no significant effect on the bond strength. In addition, the results indicate that for a successful bond it is important to choose not only a reformulated agar but a compatible irreversible hydrocolloid.