Results of stress-corrosion cracking (SCC) studies of surgical implant materials that have employed a fracture mechanics type of specimen are presented. The behavior of Type 316L stainless steel and Ti-6AI-4V ELI in a number of different environments has been examined. Tests have been performed in boiling 44% magnesium chloride solution (154°C), 5% hydrochloric acid (37°C), and physiological saline solution (37°C). Crack propagation velocity versus stress intensity curves have been obtained. Plateau velocities and threshold stress intensities have been determined. Some specimens were tested under open circuit conditions. Others were potentiostatically polarized with applied potentials similar in magnitude to those that can be generated by bioelectric effects in vivo. Propagation of stress corrosion cracks in Type 316L in physiological saline solution at 37°C was observed in situations where there was a high stress intensity and a passive film that had been disrupted by polarization.