| Actor | Actor | Number of letters | From | to | |
|---|---|---|---|---|---|
| Barth, Karl | Roulin, Alcide | 88 | 1940 | 1968 | |
| Besag, Hilde | Kirschbaum, Charlotte von | 88 | 1944 | 1965 | |
| Barth, Karl | Evangelische Missionsgesellschaft in Basel, "Basler Mission" | 87 | 1927 | 1968 | |
| Anonym | Barth, Karl | 87 | 1919 | 1968 | |
| Barth, Karl | Gogarten, Friedrich | 86 | 1919 | 1933 | |
| Barth, Karl | Goes, Helmut | 86 | 1933 | 1968 | |
| Barth, Karl | Barth, Sebastian | 86 | 1935 | 1968 | |
| Barth, Karl | Oprecht, Hans | 86 | 1935 | 1966 | |
| Barth, Karl | Senarclens, Jacques de | 86 | 1940 | 1968 | |
| Barth, Karl | Staehelin, Ernst | 85 | 1915 | 1967 | |
| Barth, Karl | Schwenzel, Liselotte | 85 | 1934 | 1968 | |
| Kirschbaum, Charlotte von | Salomon, Otto | 84 | 0 | 1950 | |
| Barth, Karl | Lindt, Karl | 84 | 1916 | 1945 | |
| Barth, Karl | Schädelin, Albert | 83 | 1909 | 1961 | |
| Barth, Karl | Takizawa, Katsumi | 83 | 1934 | 1968 | |
| Barth, Karl | Bissinger, Fritz | 82 | 0 | 1968 | |
| Barth, Karl | Huber, Karl | 81 | 1920 | 1962 | |
| Barth, Karl | Barth, Ulrich | 81 | 1927 | 1967 | |
| Bissinger, Fritz | Kirschbaum, Charlotte von | 80 | 1947 | 1963 | |
| Kirschbaum, Charlotte von | List, Hertha | 79 | 0 | 1953 | |
| Cordes, Martin Friedrich | Kirschbaum, Charlotte von | 79 | 1939 | 1959 | |
| Barth, Karl | Flückiger, Felix | 79 | 1941 | 1956 | |
| Emmerich, Kurt | Kirschbaum, Charlotte von | 78 | 0 | 1964 | |
| Kirschbaum, Charlotte von | Pilder, Maria | 78 | 1936 | 1963 | |
| Kirschbaum, Charlotte von | Netter, Maria | 78 | 0 | 1962 | |
| Barth, Karl | Küng, Hans | 78 | 1955 | 1968 | |
| Böhm, Erich | Kirschbaum, Charlotte von | 78 | 1945 | 1963 | |
| Barth, Karl | Hessel, Egon | 77 | 1927 | 1952 | |
| Barth, Karl | Sartorius, Karl August | 75 | 1900 | 1961 | |
| Barth, Karl | Lieb, Fritz | 74 | 1917 | 1966 | |
| Kirschbaum, Charlotte von | Sturm, Mathilde | 74 | 0 | 1963 | |
| Barth, Karl | Ehrenberg, Hans P. | 73 | 1919 | 1956 | |
| Barth, Karl | Ernst, Alfred | 73 | 1957 | 1968 | |
| Barth, Karl | Küppers, Erica | 72 | 0 | 1968 | |
| Barth, Karl | Barth, Nelly | 72 | 0 | 1968 | |
| Barth, Karl | Eglise Réformée de France | 72 | 1934 | 1967 | |
| Barth, Karl | Gehring, Fritz | 72 | 1947 | 1968 | |
| Barth, Karl | Stoevesandt, Hinrich | 70 | 1954 | 1968 | |
| Kirschbaum, Charlotte von | Lempp, Albert | 69 | 1927 | 1947 | |
| Barth, Karl | Lanzenstiel, Georg | 69 | 1931 | 1968 | |
| Barth, Karl | Herren, Hans | 69 | 1937 | 1943 | |
| Barth, Karl | Hirzel, Annie E. | 69 | 1957 | 1963 | |
| Barth, Karl | Schild, Paul | 67 | 1911 | 1963 | |
| Barth, Karl | Grin, Edmond | 67 | 1934 | 1965 | |
| Barth, Karl | Hromádka, Josef Lukl | 66 | 0 | 1968 | |
| Karwehl, Grete | Kirschbaum, Charlotte von | 66 | 1935 | 1964 | |
| Lentrodt, Emmy | Lentrodt, Hans | 66 | 1940 | 1941 | |
| Kirschbaum, Charlotte von | Wolf, Asta | 65 | 0 | 1965 | |
| Barth, Karl | Wedekind, Wilhelm | 64 | 1927 | 1967 | |
| Barth, Karl | Kloppenburg, Heinz | 64 | 1928 | 1968 |