Photoluminescence measurements on In1-xGaxP have verified the location of the direct-indirect conduction-band crossover at x=0.74, Eg=2.33 eV at 2 °K. The photoluminescence spectra observed are InP-like for x<0.68 and GaP-like for x>0.72. Shallow bound excitons are observed with indirect gap In1-xGaxP. Curvature in the relationship between the bound exciton energy and alloy composition suggests curvature of the indirect Γ8v-X1c band gap as a function of alloy composition (maximum deviation from the linear dependence is estimated at 22 meV). Shallow donor states seem to be tied rigidly to their conduction bands. No mixing of the Γ and X conduction-band donor ground states has been observed. Thus, significant mixing occurs over a range less than ∆x=0.02, the compositional resolution in the present measurements.