The possibility of separating the eluate and the actual biologic test for determining tissue tolerance was studied using two cements containing copper and two cements without copper. Both the materials and the two eluates obtained according to the different procedures were tested immediately. Distilled water was added to one sample of the material, and the mixture was placed in an autoclave for one hour. A second sample was leached in nutrient solution for 24 hours at 37 C. Uniform results were obtained with the copper-free material. Results with the material containing copper however varied; the results of the eluate obtained after one hour in the autoclave were different from the results obtained after 24 hours in the nutrient solution or after direct testing. The test results for the last two procedures were similar. Comparison of the two elution methods indicates that extraction in physiologic nutrient solution is better than the autoclave method using distilled water.