| Actor | Actor | Number of letters | From | to | |
|---|---|---|---|---|---|
| Barth, Heinrich | Barth, Karl | 154 | 0 | 1966 | |
| Barth, Karl | Pfändler, Marcel | 151 | 1956 | 1968 | |
| Barth, Karl | Ludwig, Gottfried | 150 | 0 | 1966 | |
| Evangelischer Verlag Zürich (EVZ) | Kirschbaum, Charlotte von | 149 | 1938 | 1965 | |
| Barth, Karl | Weber, Gotthilf | 146 | 1934 | 1967 | |
| Barth, Karl | de Quervain, Alfred | 143 | 1903 | 1968 | |
| Christian Kaiser Verlag | Kirschbaum, Charlotte von | 141 | 1927 | 1964 | |
| Kirschbaum, Charlotte von | Neumann, Elisabeth | 141 | 0 | 1965 | |
| Kirschbaum, Charlotte von | Weber, Gotthilf | 140 | 0 | 1965 | |
| Barth, Karl | Handrich, Karl | 137 | 1945 | 1968 | |
| Barth, Karl | Staewen, Gertrud | 132 | 1931 | 1968 | |
| Barth, Karl | Stoevesandt, Karl | 130 | 1923 | 1968 | |
| Barth, Karl | Traub, Hellmut | 129 | 0 | 1968 | |
| Barth, Karl | Putsch, Hugo | 125 | 1924 | 1964 | |
| Kirschbaum, Charlotte von | Schlomka sen., Lore | 125 | 0 | 1965 | |
| Bleibtreu, Otto | Kirschbaum, Charlotte von | 125 | 0 | 1958 | |
| Kirschbaum, Charlotte von | Pestalozzi, Ruth | 125 | 0 | 1962 | |
| Barth, Karl | Gollwitzer, Helmut | 123 | 1931 | 1968 | |
| Barth, Karl | Weber, Hannah | 122 | 1934 | 1962 | |
| Barth, Karl | Dehn, Günther | 120 | 1919 | 1968 | |
| Barth, Karl | Maury, Pierre | 120 | 1928 | 1955 | |
| Barth, Karl | Schlunk, Rudolf | 119 | 1927 | 1968 | |
| Barth, Karl | Schwarz, Martin | 119 | 1943 | 1968 | |
| Barth, Karl | Karwehl, Richard | 117 | 1922 | 1968 | |
| Barth, Karl | Spoendlin, Wilhelm | 116 | 1903 | 1965 | |
| Barth, Karl | von Balthasar, Hans Urs | 116 | 0 | 1968 | |
| Barth, Karl | Pestalozzi, Gerty | 115 | 1915 | 1968 | |
| Kirschbaum, Charlotte von | Slotemaker-Fischinger, Hilde | 114 | 0 | 1965 | |
| Barth, Karl | Bultmann, Rudolf | 112 | 1911 | 1966 | |
| Barth, Karl | Diem, Hermann | 111 | 1930 | 1968 | |
| Barth, Karl | Vogel, Heinrich | 110 | 1930 | 1966 | |
| Barth, Karl | Imberg, Richard | 110 | 1935 | 1959 | |
| Barth, Karl | Seifert, Katharina | 107 | 1926 | 1968 | |
| Asmussen, Hans Christian | Barth, Karl | 107 | 1925 | 1946 | |
| Barth, Karl | Vischer, Wilhelm | 106 | 1921 | 1968 | |
| Althaus, Paul | Barth, Karl | 105 | 1922 | 1966 | |
| Barth, Karl | Schweizerische Rundspruchgesellschaft SRG | 105 | 0 | 1968 | |
| Kirschbaum, Charlotte von | Vogt, Paul | 105 | 0 | 1951 | |
| Barth, Karl | Siebeck, Richard | 104 | 1920 | 1961 | |
| Barth, Karl | Wieser, Gottlob | 100 | 1910 | 1966 | |
| Barth, Karl | Sutz, Erwin | 100 | 1928 | 1968 | |
| Barth, Karl | Horn, Fritz | 98 | 1922 | 1957 | |
| Kirschbaum, Charlotte von | Merz, Monika | 98 | 0 | 1965 | |
| Barth, Karl | Miskotte, Kornelius Heiko | 98 | 0 | 1968 | |
| Barth, Karl | Casalis, Georges | 92 | 1940 | 1968 | |
| Barth, Karl | Herrenbrück, Walter | 91 | 1930 | 1968 | |
| Barth, Karl | Lentrodt, Emmy | 91 | 0 | 1942 | |
| Barth, Karl | Grobe, Emil | 90 | 1920 | 1949 | |
| Kirschbaum, Charlotte von | Thurneysen, Eduard | 89 | 0 | 1964 | |
| Barth, Karl | Oekumenischer Rat der Kirchen | 89 | 1945 | 1968 |