Capacitance-voltage profiling was used to measure interfacial polarization charge densities and conduction-band offsets at InxGa1-xN/GaN heterojunction interfaces for x = 0.054 and 0.09. A variant Of the conventional analysis technique used to deduce interface charge density and band-offset values from capacitance-voltage data was developed and applied. Conduction-band offsets of 0.09 +/- 0.07 and 0.22 +/- 0.05eV are obtained for x=0.054 and 0.09, respectively. Polarization charge densities derived from these measurements are (1.80 +/- 0.32) x 10(12) and (4.38 +/- 0.36) x 10(12) e/cm(2) for x = 0.054 and 0.09, respectively. These values are somewhat lower than those predicted theoretically, but are in good agreement with values inferred from a substantial body of optical data reported for InxGa1-xN/GaN quantum-well structures. (C) 2004 American Vacuum Society.