Organized in nine sections, plus supplements, the collection contains both personal and professional correspondence, research notes and data, manuscripts, reprints, patents, photographs. It covers his work at Cal Tech, his consulting work and professional activities, and personal and biographical materials. However, since a great deal of his government work was classified, very little remains in the collection to document his involvement with high-level decision-making, both military and civilian. Among the topics: cold-emission effect (the subject of his dissertation), nuclear physics and his work with the Kellog Laboratory in medical physics, accelerator, his wartime work with the U. S. Government and the military, the security clearance of J. Robert Oppenheimer. The collection also includes a sizeable amount of material transferred from the papers of William A. Fowler. Some of the more frequent corresponddents include: R. F. Bacher, J. W. Buchta, K. K. Darrow, L. A. DuBridge, W. A. Fowler, J. Gavin, R. H. Kent, U. Liddel, R. Oppenheimer, H. P. Robertson, J. R. Zacharias. Addition of one box of photographs (0.5 lin. ft.) donated by the Lauritsen family.