An ultrasonic diagnostic imaging system for display of 2D or 3D images comprising: an ultrasound probe having a two dimensional array transducer adapted to scan a target region with 1xN patches of elements of the array, wherein the N dimension of the patches extends in one of the elevation (Ele) or azimuth (Az) dimensions, and wherein each 1×N patch is divided into subpatches (90, 94, 98) comprising a plurality of elements less than the full N elements; a microbeamformer located in the ultrasound probe and coupled to elements of the array, wherein the microbeamformer is adapted to apply delays to signals received from each subpatch and to combine the delayed signals from each subpatch to form a partial sum signal to focus the subpatch signals from each subpatch in the N dimension; a system beamformer coupled to the ultrasound probe and adapted to receive the partial sum focused subpatch signals for each subpatch and to steer and/or focus the signals in the other of the elevation or azimuth dimensions; a beamformer controller, coupled to the microbeamformer and the system beamformer, and adapted to control, responsive to a user control, the scanning of a target region; an image processor adapted to produce, responsive to the signals steered and/or focused by the system beamformer, image data; and a display, coupled to the image processor, adapted to display a 2D or 3D image of the target region, and wherein the beamformer controller is adapted to control the microbeamformer or the system beamformer to form multilines from the partial sum signals and wherein the system beamformer is adapted to apply delays to the multilines to steer and/or focus the signals in the other of the elevation or azimuth dimensions. an ultrasound probe having a two dimensional array transducer adapted to scan a target region with 1xN patches of elements of the array, wherein the N dimension of the patches extends in one of the elevation (Ele) or azimuth (Az) dimensions, and wherein each 1×N patch is divided into subpatches (90, 94, 98) comprising a plurality of elements less than the full N elements; a microbeamformer located in the ultrasound probe and coupled to elements of the array, wherein the microbeamformer is adapted to apply delays to signals received from each subpatch and to combine the delayed signals from each subpatch to form a partial sum signal to focus the subpatch signals from each subpatch in the N dimension; a system beamformer coupled to the ultrasound probe and adapted to receive the partial sum focused subpatch signals for each subpatch and to steer and/or focus the signals in the other of the elevation or azimuth dimensions; a beamformer controller, coupled to the microbeamformer and the system beamformer, and adapted to control, responsive to a user control, the scanning of a target region; an image processor adapted to produce, responsive to the signals steered and/or focused by the system beamformer, image data; and a display, coupled to the image processor, adapted to display a 2D or 3D image of the target region, and wherein the beamformer controller is adapted to control the microbeamformer or the system beamformer to form multilines from the partial sum signals and wherein the system beamformer is adapted to apply delays to the multilines to steer and/or focus the signals in the other of the elevation or azimuth dimensions.