Abstract: Quantitative gait analysis enables clinicians to evaluate patient mobility and to diagnose a number of neuromuscular disorders. The clinical application of gait analysis is currently hampered by the high operating costs of gait laboratories. The use of instrumented footwear that performs out of the lab measurements on subjectís walking pattern is a promising way to overcome this limitation. Besides serving as assessment tools, such devices can also act as retraining tools that help regulate a patientís gait by means of acoustic or vibrotactile stimuli. At the Columbia University Robotics and Rehabilitation (ROAR) Lab, we have developed SoleSound, a fully portable instrumented footwear that can measure spatiotemporal gait parameters and deliver action-related audio-tactile feedback. This paper presents the validation of SoleSound as a tool for quantitative gait analysis. Using a reference system, we assessed the performance of SoleSound under two calibration strategies, subject-specific and generic. With the latter calibration, mean accuracy and precision (RMSESD) were 2.93+/-1.32cm for stride length, 0.70+/-0.37cm for foot-ground clearance, 1.54+/-0.70cm for step width, 4.53+/-0.90cm for foot trajectory and 4.33+/-1.01deg for ankle plantar-dorsiflexion angle. Accuracy was further improved when subject-specific calibration was used. These results indicate that SoleSound has the potential to be used for out-of-lab gait analysis.