We studied photoelectrochemical properties of AlxGa1-xN for the first time, and compared with those of InyGa1-yN. The conduction band-edge energy of n-type AlxGa1-xN decreased with Al composition, however the valence band-edge energy did not significantly change. Saturated photocurrent obtained from dynamic photocurrent-voltage measurements under illumination also decreased with increasing Al composition. Greater Al composition also shifted the onset voltage to more negative direction. These phenomena can be explained by the changes of bandgap and band-edge energies with Al composition. (c) 2006 The Electrochemical Society.