The interaction of tungsten with hydrogen peroxide was studied by Raman spectroscopy and electrochemical measurements. We found that W catalyzes the decomposition of peroxide into its ion, while the native oxide of W becomes increasingly hydrated and soluble. The decay of the peroxide concentration upon immersion of W is consistent with a model of 1-D diffusion to the W surface followed by a surface reaction with a heterogeneous rate constant of 3 x 10(-5) cm/s. This model can also be used to explain the decrease of the H2O2 solution pH and the increase in open circuit potential of W that occurs while W is immersed in H2O2.