Photoelectrochemical measurements have been carried out onp‐Si electrodes which contained islands of Pb, Cd, Au, Ni, Co, and Pt. These islands cause the photocurrent density of some of the Si systems to increase greatly (10×) in the middle region of the photocurrent potential curve. A plot of the change in potential observed for this region against log i0for the dark hydrogen evolution on the metals concerned is linear with a slope close to that expected for a rate determining step at themetal‐solution interface.