1. Two of the three metals at present in use in orthopaedic surgery have been studied to assess their tendency to cause wound reactions.

2. Cobalt-chrome alloy proved to be the better, the incidence of obligatory plate removal being at most 3 per cent. Visible corrosion in this metal never occurred.

3. 18/8 Mo stainless steel proved to be the poorer, the incidence of obligatory plate removal being 20 per cent. Visible corrosion of the metal is estimated to have occurred in about 5 per cent of screws inserted.

4. Regardless of such accelerating factors as metallic transfer, 18/8 Mo steel may have to be accepted as inherently more susceptible to corrosion than is cobalt-chrome alloy.

5. The qualities of two other stainless steels also became evident. Previous work describing the very bad situation arising from the use of EMS was confirmed. By contrast, a steel that was in use before 1951 gave little trouble. This steel was probably FSL.