These volumes, 3 and 4, of Fracture Mechanics of Ceramics con stitute the proceedings of an international symposium on the frac ture mechanics of ceramics held at the Pennsylvania State Univer sity, University Park, PA on July 27, 28, and 29, 1977. Volumes 1 and 2 were published previously as the proceedings of a sympo sium of the same name held July 11, 12, and 13, 1973, also at Penn State. All four volumes published to date concentrate on the fracture aspects of the mechanical behavior of brittle ceramics in terms of the characteristics of cracks. The program chairmen gratefully acknowledge the financial as sistance for the symposium provided by the Office of Naval Re search, the Energy Research and Development Administration, and the Army Research Office. Without their support the quality and mag nitude of this conference simply would not have been possible. Numerous individuals contributed to the success of the con ference, but unfortunately they cannot all be listed here. However the program chairmen would especially like to recognize the contri butions of Penn State Conference Coordinator, Mr. Ronald Avillion, whose expertise in planning and organization was indispensable; Dr. Fred R. Matson for his interesting after dinner speech; and Drs. A. M. Diness, J. C. Hurt, and D. W. Readey for their en couragement and valuable suggestions regarding the program. Finally, we wish to also thank our joint secretaries for the patience and help in bringing these proceedings to press.