Cobalt—chromium alloy implants were placed subcutaneously in the neck region of mice, and the animals were killed after 8 weeks. The cobalt concentration was high in the connective tissue of the capsule formed around 5 out of 10 cobalt—chromium implants. In nine other tissues analyzed no statistically significant increases in the cobalt concentration were detected. The surgical procedure and the carrying of an implant did not influence the weight increase of the animals during the period of the experiment.