Microcalcification is the precursor of vulnerability of plaques in humans. Visualization of such small structures in vivo with high spatial resolution is an unsolved issue. The goal of this study is to evaluate the potential of scanning acoustic microscopy (SAM) in the determination of atherosclerotic plaques with calcifications by validating this technique with micro-computer tomography (micro-CT), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The fibrocalcific plaques were obtained from 12 different patients and initially examined with micro-CT. The images exhibited calcifications within these plaques. For imaging with SAM, approximately 5 mu m thick slices were prepared. Sound speed values within calcified regions were measured to be greater than the ones in collagen-rich regions. These fibrocalcific plaques were also examined with SEM and EDS revealing collagen and calcium deposition within these samples. The consistency of the results obtained by all of the modalities involved in our study is an indication of the potential of SAM as a clinical tool for the diagnosis of vulnerable plaques.