Abstract: A radiopaque composition and implant comprising a mixture of a polymer, such as polyetherketone (PEEK), polyetherketone (PEK), polyetherketoneketone (PEKK), polyetherimide, or polyphenylsulfone, and bismuth trioxide (BiO3) is provided. The mixture comprises BiO3 of about twenty to thirty percent (20% to 30%) by weight. The composition is useful in radiopaque implants for mammals including humans, such as in catheters, stents, screws, anchors, dental caps and posts, bone and joint replacements, and the like. The composition is also useful for radiopaque markers in implants and for radiopaque articles used in surgical and other in vivo procedures. The radiopaque items can be easily identified and located in a patient's body via X-ray examination or fluoroscopy.