| Marx to Hugo Heller. 29 January |
| Engels to Johann Philipp Becker. 30 January |
| Engels to Wilhelm Liebknecht. 1 March |
| Marx to Nikolai Danielson. 10 April |
| Marx to Rudolph Meyer. 28 May |
| Engels to J Gugenheim. 16 June |
| Engels to Eduard Bernstein. 17 June |
| Engels to Eduard Bernstein. 26 June |
| Engels to Johann Philipp Becker. 1 July |
| Marx to Carlo Cafiero. 29 July |
| Engels to August Bebel. 4 August |
| Marx to Rudolph Meyer. 7 August |
| Marx to Engels. 14 August [abstract] |
| Marx to Jenny Longuet. 19 August |
| Engels to Marx. 20 August |
| Engels to Marx. 25 August |
| Marx to Engels. 25 August |
| Engels to Marx. 26 August |
| Engels to Karl Hochberg. 26 August |
| Marx to Engels. 27 August |
| Marx to Engels. 28 August |
| Marx to Engels. 3 September |
| Engels to Johann Philipp Becker. 8 September |
| Marx to Engels. 9 September |
| Engels to Marx. 9 September |
| Marx to Engels. 10 September |
| Engels to Marx. 11 September |
| Marx to Engels. 11 September |
| Marx to Engels. 14 September |
| Engels to Johann Philipp Becker. 15 September |
| Marx and Engels to August Bebel, Wilhelm Liebknecht, Wilhelm Bracke and Others (Circular Letter). 17-18 September |
| Marx to Carl Hirsch. 18 September |
| Marx to Nikolai Danielson. 19 September |
| Marx to Friedrich Adolph Sorge. 19 September |
| Engels to Johann Philipp Becker. 24 September |
| Engels to Marx. c. 8 October |
| Marx to Bertha August. 25 October |
| Engels to August Bebel. 14 November |
| Marx to Friedrich Adolph Sorge. 14 November |
| Engels to August Bebel. 24 November |
| Marx to Achille Loria. 3 December |
| Marx to an Unknown Correspondent. 11 December |
| Marx to Charles Walstone (Waldstein). 13 December |
| Engels to Thomas Allsop. 14 December |
| Engels to August Bebel. 16 December |
| Engels to Johann Philipp Becker. 19 December |
| Engels to Amelie Engels. c. 1879-1880 |