Ponencia presentada en el XIX Congreso Internacional de Acústica (ICA2007), Madrid, 2-7 Sep 2007.-- PACS: 43.20.Gp.A theoretical and computational study of the propagation of ultrasonic pulses in a fat-muscle-bone biological multilayer is presented. The different layers are considered as homogeneous tissues with frequency dependent attenuation and plane parallel interfaces. Fat and muscle are considered as viscous fluids while bone is considered as viscoelastic solid. Specific propagation parameters and values of layer thickness are adopted from practical cases of interest in ultrasonic therapeutic (diathermy) applications. Numerical simulation of ultrasonic pulse propagation in this multilayer structure is made with time domain finite differences method. Ultrasonic reflection and transmission coefficients at the fluid/fluid and fluid/solid interfaces, for monochromatic plane-wave propagation, are analytically computed for arbitrary incidence angles below the first critical angle. Reflection and transmission characteristics at the interfaces were also obtained from numerical simulation of broad band ultrasonic pulse propagation, computed from peak amplitudes of ultrasonic incident, reflected and transmitted pulses. Reflection and transmission at different interfaces, pulse reverberation, reflection at soft interfaces and generation of shear waves at the bone are studied.This work has been supported by the European Program ALFA Nº I-0343-FA-FCD-FI (PETRA II), the Spanish MEC, R&D Project CICYT Ref. DPI2005-00124 of the I+D National Plan, and by and by CYTED/CNPq (PULSETS).Peer reviewed