We present the dynamic behavior of unidirectional S-2 glass/SC-15 composites at confining pressure up to 100 MPa. The experiments were conducted by using a conventional Kolsky compression bar modified by adding a radial and axial confining chamber. Prior to the dynamic loading, hydraulic pressure was applied to the two chambers simultaneously. The radial chamber enclosed the cylindrical composite specimen and applied the radial confining pressure. On the other hand, the axial chamber was added at the free end of the transmission bar, providing the axial portion of the hydrostatic pressure to the specimen. Once the triaxial confinement was achieved, a striker impacted the incident bar to apply a dynamic compressive load to the specimen. Dynamic results were compared to the high-rate unconfined experiments, and the effects of load rate and confining pressure on the dynamic behavior of composites were discussed.