The synthesis of gold, palladium, and gold-palladium alloy nanoshells (approximately 15-20 nm thickness) was accomplished by the reduction of gold and palladium ions onto dielectric silica core particles (approximately 100 nm in diameter) seeded with small gold nanoparticles (approximately 2-3 nm in diameter). The size, morphology, elemental composition, and optical properties of the nanoshells were characterized using field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and ultraviolet-visible spectroscopy. The results demonstrate the successful growth of gold, palladium, and gold-palladium alloy nanoshells, where the optical properties systematically vary with the relative content of gold and palladium. The alloy nanoshells are being prepared for use in applications that stand to benefit from photoenhanced catalysis.