Purpose: The purpose of this in vitro study was to determine whether there is a correlation between the speed of sound (SOS), as measured by quantitative ultrasound (QUS), and bone quality, as expressed in Hounsfield units (HU) measured by spiral computed tomography in the mandible. Materials and Methods: Dry human mandibles (n = 23) with 69 regions of interest (ROIs) were selected for QUS and computed tomographic measurements of SOS and HU, respectively. The three ROIs defined in each mandible were the right canine, left canine, and central incisor regions. A time-of-flight approach was used to establish the SOS through bone. The mean HU value derived from scanned computed tomographic images of each ROI was evaluated for correlation with SOS. Results: The Spearman rho test revealed a modest but significant correlation between SOS and HU (R2 quadratic = 0.339, P .01). Conclusion: In this in vitro study conducted in dry human mandibles, a statistically significant correlation was identified between QUS and HU. Keywords: bone quality, Hounsfield units, quantitative ultrasound, speed of sound