Energy-dispersive x-ray-diffraction studies were carried out on the III-V compound BP to megabar pressures using diamond-anvil techniques and a high-energy synchrotron x-ray source. The BP sample remained stable in its zinc-blende phase to at least 110 GPa, the upper pressure limit of this experiment. The equation-of-state and Birch coefficients of BP were obtained from this experiment. The measured bulk modulus of BP is slightly lower than the value obtained in recent theoretical calculations based on the total energy pseudopotential method within the local-density approximation.