This paper presents ultrasound elastography results obtained with a 640-element array transducer we have recently developed. This probe allows the acquisition of series of three adjacent imaging planes over time and therefore makes possible the computation of 2-D elastograms, with consideration of out-of-plane motion. In this study, elastography experiments were conducted on phantoms and bovine tissue samples, and compression was manually applied to the media via the hand-held ultrasound transducer. The results obtained with the proposed data acquisition and 3-D processing are presented and compared to those from a classical 2-D approach.