Band gap measurements have been performed on strainedInxGa1−xNepilayers withx⩽0.12.The experimental data indicate that the bowing of the band gap is much larger than commonly assumed. We have performed first-principles calculations for the band gap as a function of alloy composition and find that the bowing is strongly composition dependent. Atx=0.125the calculated bowing parameter isb=3.5 eV,in good agreement with the experimental values. ©1998 American Institute of Physics.