1. A method is described for comparison of metallic substances with reference to their capacity to evoke inflammation when used subcutaneously. 2. Powders of the test metal may be compared with similar powders of other umetals by injecting suspensions of them into animals and examining the histological reaction at intervals. 3. By this method, very fine powders of several substances including type 316 stainless steel, and a cobalt chromium alloy were compared. All showed some degree of reaction, the least being evoked by the cobalt chrome alloy.