Ultrasound imaging of soft tissues places severe demands on the design of imaging systems because of the large range of echo amplitudes which may be encountered at any point in the body. Simple TGC curves are often inadequate in producing optimum gray scale images since the ultrasound traverses a variety of structures with substantially different attenuation coefficients. Phased array systems are shown to suffer from increased image ambiguity as compared to simple transducers, a result of discrete sampling of the aperture, which reduces the effective dynamic range which can be presented accurately. For a 16 element 1.7MHz array with 1.76 wavelengths inter-element spacing the maximum sidelobes are only 6db below the main lobe. The use of different transmit and receive array geometries can improve the overall system spatial response. Experimental results from a 16 element 1.7 MHz transmit array with.88 wavelength inter-element spacing and a receive array of the same frequency with 1.76 wavelength spacing indicated a reduction in the sidelobes to 13db below that of the main beam. © 1976 SPIE.