Tests are reported on bacterial growth and inhibition in vitro in the presence of substances used as implant materials: surgical silver, iron, zinc-coated galvanized iron, aluminum alloy, stainless steel, Vitallium, and methyl methacrylate. The results showed: 1) metals that have low grades of tissue reactivity and little bacteriotoxic effect provided a framework along which bacterial growth and propagation occurred; 2)metals that have higher levels of cellular reactivity, specifically aluminum and galvanized wire, caused selective bacterial toxicity. The in vitro response of bacteria to methyl methacrylate was similar to that of Vitallium and other inert substances, i. e. , growth and propagation were abundant adjacent to methyl methacrylate. These studies have led to the speculation that, if similar phenomena occur in vivo, bacterial growth ahd dissemination might be increased when an inert implant material was used and decreased when the implant material was more reactive.