The magnetic ordering structure of GdPO 4 is determined at T= 60 mK by the diffraction of hot neutrons with wavelength λ= 0.4696 Å. It corresponds to a noncollinear antiferromagnetic arrangement of the Gd moments with propagation vector k=(1/2, 0, 1/2). This arrangement is found to minimize the dipole-dipole interaction and the crystal-field anisotropy energy, the magnetic superexchange being much smaller. The intensity of the magnetic reflections decreases with increasing temperature and vanishes at T≈ 0.8 K, in agreement with the magnetic ordering temperature T N= 0.77 K, as reported in previous works based on heat capacity and magnetic susceptibility measurements. The magnetocaloric parameters have been determined from heat capacity data at constant applied fields up to 7 T, as well as from isothermal magnetization data. The magnetocaloric effect, for a field change Δ B= 0− 7 T, reaches− Δ S T …