Carbon-carbon fiber composite is interesting for surgical implantation due to high strength, combined with low modulus of elasticity and biocompatibility. The tantalum coated C-C cages for spinal fusion presented in this paper offers excellent bone ingrowth and inherent X-ray marking while preserving the desirable properties of the C-C substrate: Strength, toughness, low E-modulus, and radiolucence. The radiolucence is maintained by applying a thin (<5mm), uniform tantalum coating. A pilot series of tantalum coated C-C spinal cage implants was tested with respect to mechanical properties, compatibility with diagnostic imaging and by implantation in a porcine model. Mechanical testing demonstrated adequate strength for carrying the load of the spine and endurance of handling during surgery. Compatibility with diagnostic imaging techniques was demonstrated for radiology and CT. Spinal implantation (porcine model) verified adequate strength, biocompatibility, bone ingrowth and compatibility with radiology and CT-scanning, both producing clear images of the implant and bone ingrowth inside the implant.