Biographical material includes correspondence and papers relating to Lonsdale's imprisonment; diaries and personal notebooks, 1946-1969; letters and photographs. Research material covers years 1924-1970 and is in two sub-sections. Royal Institution papers include notebooks, correspondence with colleagues such as W.H. Bragg and J.M. Robertson; notes and drafts on various research topics, including diffuse scattering of X-rays, thermal vibrations in crystals, methonium compounds and urinary calculi, the latter being well documented with several case studies; photographs, mostly of X-ray diffraction patterns. The University College London papers included teaching and administrative work; documentation relating to laboratory personnel, research funding, and the 'Round Table on Peace Studies.' Publications, lectures and broadcast materials are extensive, including drafts of articles, books, book reviews, obituaries, and letters to newspapers and magazines; subjects include peace and religious issues; atomic weapons; ethics and role of science in society; religion; work on the International Tables for Crystal Structure Determination. There is extensive documentation of Lonsdale's visits and conferences, 1943-1971, which often included her other interests; her association with twenty-two societies and organizations is documented, including the British Association for the Advancement of Science and the International Union of Crystallography; the Pugwash Conferences on World Affairs, 1948-1970; and papers on prison reform. Correspondence covers the years 1927-1974, and consists of two main sequences, one arranged alphabetically and the other chronologically. This series includes important early letters, 1927-1929; and day files of outgoing correspondence, 1966-1969. Correspondents include Max Born, W.H. Bragg, W.L. Bragg, E.G. Cox, P.P. Ewald, D.M.C. Hodgkin, H.J. Milledge, L.C. Pauling and A.J.C. Wilson. (Index of correspondents included.)