We have assessed the effect of a variety of implants commonly used in fracture fixation and joint replacement on the activation of metal detectors at airport security gates. A volunteer with metal implants strapped on and patients with implants in situ walked through the device. Implants used in fixation do not activate it, except for Richards cannulated screws. An Austin-Moore prosthesis does set off the detector, but a single joint replacement does not. Three or four joint replacements activate the alarm and patients with these implants should be warned of this possibility