There are letters from fellow historians, such as John Franklin Jameson and Aleksandr Lappo-Danilevskiĭ; Kadet Party leaders, including Vladimir D. Nabokov and Nikolaĭ Astrov; and others such as Boris Bakhmeteff, Charles Crane, Vladimir Jabotinsky, Louis Marshall, Thomas Masaryk, and Nikolaĭ Roerich. A large correspondence series consists of letters and petitions sent to Miliukov during the Third State Duma (1907-12). Manuscripts include Mili︠u︡kov's memoirs, and his notebooks from the period of the Civil War. There is also a manuscript by Isaak Shkovskiĭ (pseudonym -- Dioneo) on Russian writers and journalists during World War I. Subject files deal with the State Duma, the Civil War, and the emigration.

Most of the collection concerns the Russian emigration in interwar Europe; a sizeable part deals with the Kadet (Constitutional Democrat) Party in the Russian Civil War. There is correspondence, manuscripts, subject files, photographs, and printed materials. There are many letters by liberal figures, such as Astrov, Viktor Chelishchev, Petr I︠U︡renev, Aleksandr Kizevetter, Pavel Mili︠u︡kov, Vladimir D. Nabokov, Vladimir Obolenskiĭ, Panina, and Ivan Petrunkevich. There are also letters from Ivan Bilibin, Alice Masaryk, and Thomas Masaryk. Manuscripts are chiefly by Astrov, and include memoirs, poems, and lectures. There are also memoirs by Panina, and eulogies by various people on Astrov. Subject files from 1917-1920 have materials on Panina's arrest and trial by the Bolsheviks, Kadet conferences, protocols of meetings of the Kadet Party central committee, and other items. Files on the emigration deal with the Russkiĭ Ochag (Russian Hearth) and other bodies, especially in Czechoslovakia. There are photographs of Astrov, Kizevetter, Nikodim Kondakov, Alice Masaryk, Panina, and others. Printed materials include books, clippings, and offprints by Astrov and others.