The crystal structure of magnetoelec. KNiPO4 was refined by single crystal x-ray diffraction methods at room temp. confirming orthorhombic space group Pna21. Powder neutron diffraction studies showed that the room temp. structure is preserved down to 30 K. Consistent with magnetic susceptibility measurements, long-range antiferromagnetic ordering according to K = 0 and Shubnikov space group Pna21 is established by neutron diffraction at temps. below TN = (25.5+-0.5) K. The ordered magnetic moments of (3.00 +- 0.04) mB, oriented along [1, 0, 0], indicate large orbital contributions to the magnetic moments of Ni2+. DTA studies at 100-1000 Deg, showed two phase transitions, at 486.5 Deg and at 581.3 Deg. [on SciFinder (R)]