Deformation and failure characteristics of two metal-glass interpenetrating phase composite (IPC) systems were compared against a single-phase glass control. The first system (Captek-P) comprised an interleaved arrangement of flake-shaped Au/Pt/Pd particles, the second (Captek-G) comprised loosely packed spherical Au particles. Both materials contained a fully interconnected network of porosity, formed by thermal fusion of particles at contact points. Glass was infiltrated into the porous networks by capillary action at high temperature. Mechanical properties were evaluated using three-point bend tests and compared to data from the glass control. The strength of the glass control (123.47 MPa) was not significantly different to that of either IPC, however both Captek-P and Captek-G IPCs displayed significantly reduced elastic moduli (55.2 +/- 10.6 GPa and 48.4 +/- 12.4 GPa respectively) compared with the glass (91.5 +/- 9.6 GPa). In addition to significantly higher relative toughness than the glass control the IPC materials exhibit plastic deformation prior to failure. Mixed fracture modes were evident on fracture surfaces. Corresponding stress-strain profiles for the materials show well-defined linear elastic regions that make a gradual transition into plastic behaviour. Strength of the glass control decreased by 28% upon exposure to moisture, a feature echoed by the Captek-G IPC system, however not by the Captek-P IPC, indicating that the morphology of the interpenetrating reinforcement can significantly affect the mechanical properties of IPCs. (C) 2002 Kluwer Academic Publishers.