Ultrasound is a women friendly breast cancer examination method. To facilitate the design of new imaging modalities and imaging algorithms, software is required to compute the transient acoustic pressure wave field in inhomogeneous media. A frequency domain integral equation is formulated to model attenuative acoustic wave fields in three-dimensional breast models. The method allows for multiple scattering caused by inhomogeneities in the speed of sound and attenuation. The resulting integral equation is solved using an iterative conjugate gradient scheme. The accuracy of the method is tested by comparing a plane wave scattering off a spherical contrast to an analytical solution. In addition, various simulations are performed to investigate the effect of inhomogenities in the speed of sound and attenuation on A-scans.@en