| Marx to Charles Longuet. 4 January |
| Marx to an Unknown Correspondent. 31 January |
| Engels to Karl Kautsky. 1 February |
| Engels to Eduard Bernstein. 2 February |
| Marx to Carl Pearson. 15 February |
| Marx to Nikolai Danielson. 19 February |
| Marx to Ferdinand Domela Nieuwenhuis. 22 February |
| Engels to Jenny Longuet. 24 February |
| Marx to Vera Zasulich. 8 March |
| Engels to S F Kaufmann. 11 March |
| Engels to Eduard Bernstein. 12 March |
| Engels to Johann Philipp Becker. 28 March |
| Engels to August Bebel. 30 March |
| Engels to Gottlieb Lemcke. 2 April |
| Engels to Johann Philipp Becker. 4 April |
| Marx to Jenny Longuet. 11 April |
| Engels to Eduard Bernstein. 14 April |
| Engels to August Bebel. 28 April |
| Marx to Jenny Longuet. 29 April |
| Engels to Jenny Longuet. 31 May |
| Marx to John Swinton. 2 June |
| Marx to Friedrich Adolph Sorge. 2 June |
| Engels to Friedrich Adolph Sorge. 2 June |
| Marx to Jenny Longuet. 6 June |
| Engels to Jenny Longuet. 17 June |
| Marx to Friedrich Adolph Sorge. 20 June |
| Marx to Henry Mayers Hyndman. 2 July |
| Engels to Marx. 7 July |
| Engels to Norris A Clowes. 22 July |
| Marx to Jenny Longuet. 22 July |
| Marx to Engels. 27 July |
| Engels to Marx. 29 July |
| Marx to Engels. 3 August |
| Engels to Marx. 6 August |
| Marx to Carl Hirsch. 6 August |
| Marx to Engels. 9 August |
| Marx to Laura Lafargue. 9 August |
| Engels to George Shipton. 10 August |
| Engels To Marx. 10 August |
| Engels to Marx. 11 August |
| Engels to George Shipton. 15 August |
| Marx to Engels. 16 August |
| Marx to Pyotr Lavrov. 16 August |
| Engels to Marx. 17 August. |
| Engels to Eduard Bernstein. 17 August |
| Engels to Marx. 18 August |
| Marx to Engels. 18 August |
| Marx to Jenny Longuet. 18 August |
| Marx to Engels. 19 August |
| Marx to Jenny Longuet. 20 August |
| Engels to August Bebel. 25 August |
| Engels to Karl Kautsky. 27 August |
| Marx to Karl Kautsky. 1 October |
| 88 Marx to Minna Kautsky. 1 October |
| Engels to Eduard Bernstein. 25 October |
| Engels to Johann Philipp Becker. 4 November |
| Engels to Eduard Bernstein. 30 November |
| Marx to Jenny Longuet. 7 December |
| Marx to Johann Philipp Becker. 10 December |
| Marx to Nikolai Danielson. 13 December |
| Marx to Friedrich Adolph Sorge. 15 December |
| Marx to Jenny Languet. 17 December |
| Engels to Karl Kautsky. 18 December |
| Engels to Ferdinand Domela Nieuwenhuis. 29 December |
| Marx to Roland Daniels. 31 December |
| Engels to Lev Hartmann. end December |