The first observations of a high energy ion shock spike extending in energy to >25 MeV for protons, >4.3 MeV/nuc for alpha particles, and >1.6 MeV/nuc for medium nuclei with Z?S6 are reported. The measurements were obtained in the course of a solar particle event on September 15, 1974 by The Johns Hopkins University/Applied Physics Laboratory (JHU/APL) experiments on the IMP-7 and IMP-8 spacecraft. It is shown that the observations can be reasonably accounted for by intensive acceleration of charged particles at an ''almost'' perpendicular interplanetary shock wave. The data are inconsistent with a one-step d.c.-type acceleration process.