| Engels to Wilhelm Liebknecht. 10 January |
| Marx to Charles Walstone (Waldstein). 26 January |
| Engels to Carl Hirsch. 17 February |
| Marx to Bernhard Kraus. 26 March |
| Engels to Johann Philipp Becker. 1 April |
| Engels to H Meyer. 3 April |
| Engels to August Bebel. After 27 April |
| Engels to Paul Lafargue. 4 May |
| Marx to Paul Lafargue. c. 4-5 May |
| Marx to Ferdinand Domela Nieuwenhuis. 27 June |
| Engels to Minna Gorbunova. 22 July |
| Marx to Philip Stephen King. 27 July |
| Engels to Minna Gorbunova. 2 August |
| Engels to Minna Gorbunova. 5 August |
| Marx to John Swinton. 15 August |
| Engels to Johann Philipp Becker. 17 August |
| Marx to Friedrich Adolph Sorge. 30 August.. |
| Engels to Laura Lafargue. 3 September |
| Marx to Paul Lafargue. 3 September |
| Engels to Paul Lafargue. 9 September |
| Marx to Nikolai Danielson. 12 September |
| Engels to Paul Lafargue. 12 September |
| Engels to Marx. 13 September |
| Marx to Ferdinand Fleckles. 29 September |
| Engels to Eugen Oswald and an Unknown Correspondent. 5 October |
| Engels to Johann Philipp Becker. 12 October |
| Engels to Harry Kaulitz. 28 October |
| Marx to John Swinton. 4 November |
| Marx to Friedrich Adolph Sorge. 5 November |
| Marx to Friedrich Adolph Sorge. 5 November |
| Marx to Ferdinand Fleckles. 12 November |
| Marx to Achille Loria. 13 November |
| Marx to Henry Mayers Hyndman. 8 December |
| Engels to Johann Philipp Becker. 24 December |
| Marx to Carl Hirsch. 29 December |