The fully digital three-dimensional (3D)/(4D: 3D+time) ultrasound system technology of this chapter consists of an advanced beamforming structure that allows the implementation of adaptive and synthetic aperture signal processing techniques in ultrasound systems deploying multidimensional arrays of sensors. The aim with this fully digital ultrasound beamformer is to address the fundamental image resolution problems of current ultra-sound systems and to provide suggestions for its implementation into existing 2D and/or 3D ultrasound systems as well as develop a complete stand-alone 3D ultrasound solution. This development has received grant support from the Defence R&D Canada (DRDC) and from the European Commission IST Program (i.e., ADUMS project: EC-IST-2001-34088).