The equation of state of δ-AlOOH was investigated using powder X-ray diffraction up to 17 GPa. Measurement of the volume at 300 K gave a value of the bulk modulus of K0 = 124(2) GPa, whereas its pressure derivative was K′ = 13.5(7). The b axis of the unit cell is more compressible than the a and c axes - in agreement with a neutron diffraction study at high pressure by Sano-Furukawa et al. (2008). Measurements presented here show that δ-AlOOH has a compressibility 200% higher than in the previously reported equation of state by Vanpeteghem et al. (2002).