The design, fabrication and evaluation of twodimensional transducer arrays are described for medical ultrasound imaging. A 4 x 32, 2.8 MHz array was developed to use new signal processing techniques for improved B-scan imaging including elevation focusing, phase correction and synthetic aperture imaging. Laboratory measurements from typical array elements showed 50 Ω insertion loss of-56 dB,-6 dB fractional bandwidth of 43%, interelement cross-talk of-19 dB, and-6 dB pulse-echo angular response of 62°. Several 16 × 16 arrays have also been developed for high speed volumetric imaging. These include 96 transmit elements and 32 receive channels. With a λ/4 matching layer, laboratory measurements show 50 Ω insertion loss of-72 dB,-6 dB fractional band-width of 63%, inter-element cross-talk of-29 dB and-6 dB angular response of 25°. In vivo cardiac, abdominal, and obstetric B-scans with elevation focusing have been obtained, as well as high speed C-scans, with these 2-D arrays.