The direct E,, E, + A , and indirect E r -x transition energies of Ini-,Ga,P crystals are studied by electromodulation and wavelength modulation methods a t 77 K and room temperature. TheE, energy at 77 K and room temperature obeys a parabolic relation as a function of composition x with a bowing parameter of b = 0.764 and 0.76 eV, respectively. The E r -x energy a t 77 K can be expressed by a linear x-dependence with slope 0.072 eV. The crossover point a t 77 K is determined as xc = 0.72 0.015; E , = (2.300 f 0.003) eV. The spin-orbit splitting A, shows an upward bowing with bowing parameter -0.060 eV.