We report high-pressure photoluminescence experiments up to 80kbar at 2K on ordered and disordered GaInP nominally lattice matched to GaAs. The initial band-gap reduction between the two samples due to ordering effects is 86 +/- 5 meV. The direct band-gap energy of both samples under pressure increases linearly at rates of 7.3 +/- 0.1 and 8.4 +/-0.1 meV/kbar, respectively. At high pressure the conduction band X minima are clearly observed allowing their pressure dependence to be directly measured. An earlier study reported that the X and F conduction band minima are lowered in energy by the same amount with respect to the disordered phase. Our results clearly show that the ambient pressure separation between the X and F conduction band minima is 57 +/- 20 meV higher in the ordered. We review previous results and show that the absolute energy of the X minima appears to remain constant with ordering, assuming a valence band increase in energy. (C) 2004 Elsevier B.V. All rights reserved.