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The magnitude of early age shrinkage of Ultra High Performance Concrete (UHPC) is markedly different from normal and high strength concretes. A series of experiments were performed to determine the influence of water to binder ratio and silica fume content on the rate of hydration, stiffness development, chemical and external shrinkage under both sealed and unsealed conditions. Experimental apparatus, designed for shrinkage in normal strength concretes, were adapted to accommodate the larger volume changes and minimise the influence of boundary restraint. Continuously monitored internal temperature, and relative humidity conditions, along with periodic measurements of hydration degree and stiffness are used to elucidate the volumetric deformation mechanisms. Results, from as early as three hours after water addition demonstrate significant volumetric changes occurring in the early plastic state of the material.