The magnetostriction of the intermetallic antiferromagnet Au2Mn was measured up to a magnetic field intensity of 80 kOe in the temperature range from room temperature to He point. Both the longitudinal and transversal magnetostriction curves consist of (1) a fairly complicated part in the low magnetic field range, (2) followed by a contraction of the order of 200×10−6, then (3) a weak contraction proportional to the magnetic field intensity at high fields. Above 200°K, slight expansion can be seen, in the case of longitudinal effect, between states (2) and (3). The present compound Au2Mn has a tetragonal lattice with a magnetic structure of screw arrangement. The observed magnetostriction can be explained by assuming a superposition of (1) magnetostriction due to the rotation of the magnetic moment in the c plane, (2) that due to its rotation toward the c axis, (3) exchange magnetostriction due to the change of screw angle during the course of magnetisation, and (4) forced magnetostriction due to the change of the moment caused by the action of the magnetic field.