Quantitative ultrasound (QUS) techniques make use of frequency-dependent information from backscattered echoes normally discarded in conventional B-mode imaging. Using scattering models and spectral fit methods, properties of tissue microstructure can be estimated. The use of full angular spatial compounding has been proposed as a means of improving the variance of scatterer property estimates and spatial resolution of QUS imaging. In this work, preliminary experimental results from a QUS implementation on an ultrasonic breast tomography scanner from TechniScan, Inc. are presented. The imaging target consisted of a cylindrical gelatin phantom of 7.8 cm diameter. The phantom contained uniformly distributed glass bead inclusions of 85 m mean diameter. The scanner provided reflection-mode data using arrays with 6 MHz nominal center frequency for 17 different angles of view distributed between 0° and 360°. Tomographic images of speed of sound were also generated by the scanner and used for refraction-compensation and registration of the effective scatterer diameter (ESD) estimates corresponding to ROIs at different angles of view. Only data from the surface of the array to the center of the tomography gantry were analyzed for each angle of view, which resulted in 8.5 effective angles of view per ROI. ESD estimates were obtained using ROIs of size 4 mm by 4 mm with a 50% overlap. The average mean and standard deviation of the single angle of view estimates considering the 17 data sets were 85.4 μm and 12.2 μm, respectively. The resulting ESD mean and standard deviation of the compounded image were 85.2 μm and 4.1 μm, respectively. The preliminary experimental results presented here represent the first implementation of QUS on an ultrasonic breast tomography scanner and demonstrate some of the benefits of integrating these technologies, i.e., the availability of full angular spatial compounding and integration with tomographic speed of sound images. ©2009 IEEE.