Abstract: A high-frequency diffraction problem is considered for a plane wave incident on a three-axis strongly elongated ellipsoid. The leading order term of the asymptotics of the field in a boundary layer near the surface is constructed with the use of the parabolic equation method in ellipsoidal coordinates. The field is expressed in the form of the integral via the solutions of the confluent Heun equation. The values of the field on the surface of an absolutely hard ellipsoid and the velocities on the absolutely soft ellipsoid are computed. The effects of high-frequency diffraction are discussed.