ACKNOWLEDGMENTS Shock-pressure measurements for Operation Ivy were planned by representatives of JDivision of the Los Alamos Scientific Laboratory and the Weapons Effects Department (5110) of Sandia Corporation. The author wishes to express his appreciation for the fine cooperation among the participating agencies and the personnel and contractorsof the Pacific Proving Grounds. Installation of the measuring equipment and field measurements were ably executed by personnel of the Pacific Proving Ground Division (5233) of the Field Test Organization of the Sandia Corporation. A List of all participating personnel is presented as Appendix B to this report. The author wishes to acknowledge also the assistance of Miss Sally Langenstein in preparing this manuscript for issuance.