Ultrasound is useful in evaluating the integrity of silicone breast implants. However, extensive operator experience is required. A system for computer-assisted diagnosis is being developed to reduce operator dependence. Feasibility was examined by measuring the ultrasonic properties of breast implants in vitro. Silicone gels from 45 explanted implants (26 intact and 19 ruptured) were placed in sealed acoustic test chambers and 60 RF A-lines were acquired from each. Velocity of sound, attenuation and integrated backscatter (IB) were estimated. Receiver operating characteristic (ROC) analysis was performed. The mean speed of sound was 1060 m/s +/- 50.1 m/s in intact implants and 1115 m/s +/- 74.3 m/s in ruptured ones (p < 0.003). Differences in attenuation were not statistically significant. The mean IB was -83.9 dB +/- 7.94 dB in intact and -77.2 dB +/- 9.07 dB in ruptured implants (p < 0.006). The area under the ROC curve (Az) was 0.70 and 0.73 for IB and velocity, respectively, while combining the two yielded Az = 0.81. Changes in speed of sound and IB, with changes in integrity of breast implants, have been demonstrated in vitro. The results indicate the potential for quantitative assessment of silicone breast implants performed in vivo.