| Marx to Laura Lafargue. 4 January |
| Marx to Engels. 5 January |
| Engels to Eduard Bernstein. 6 January |
| Engels to Marx. 8 January |
| Marx to Engels. 12 January |
| Engels to Emil Engels. 12 January |
| Marx to Amalie Daniels. 12 January |
| Engels to Marx. 13 January |
| Marx to Engels. 15 January |
| Marx to Pyotr Lavrov. 23 January |
| Engels to Eduard Bernstein. 31 January |
| Engels to Karl Kautsky. 7 February |
| Engels to Johann Philipp Becker. 10 February |
| Marx to Engels. 17 February |
| Engels to Pyotr Lavrov. 18 February |
| Marx to Engels. 2 February |
| Engels to Eduard Bernstein. 22 February |
| Engels to Pyotr Lavrov. 23 February |
| Marx to Jenny Longuet. 23 February |
| Marx to Engels. 1 March |
| Marx to Engels. 3 March |
| Engels to Eduard Bernstein. 10 March |
| Marx to Jenny Longuet. 16 March |
| Marx to Paul Lafargue. 20 March |
| Marx to Engels. 23 March |
| Marx to Jenny Longuet. 27 March |
| Marx to Engels. 28-31 March |
| Engels to Henry Mayers Hyndman. c. 31 March |
| Marx to Engels. 4 April |
| Marx to Jenny Longuet. 7 April |
| Marx to Engels. 8 April |
| Engels to Pyotr Lavrov. 10 April |
| Engels to Berthold Sparr. 12 April |
| Engels to Friedrich Adolph Sorge. 13 April |
| Marx to Laura Lafargue. 14 April |
| Engels to Eduard Bernstein. 17 April |
| Marx to Engels. 18 April |
| Engels to Eduard Bernstein. 21 April |
| Marx to Engels. 28 April |
| Marx to Jenny Longuet. 28 April |
| Engels to Eduard Bernstein. 3 May |
| Marx to Laura Lafargue. 6 May |
| Marx to Engels. 8 May |
| Marx to Jenny Longuet. 8 May |
| Engels to Eduard Bernstein. 10 May |
| Engels to August Bebel. 10 May |
| Marx to Engels. 20 May |
| Marx to Eleanor Marx. 21 May |
| Marx to Jenny Longuet. 26 May |
| Marx to Eleanor Marx. 28 May |
| Marx to Engels. 30 May |
| Marx to Jenny Longuet. 4 June |
| Marx to Engels. 5 June |
| Marx to Engels. 9 June |
| Marx to Engels. 16 June |
| Marx to Laura Lafargue. 17 June |
| Engels to Friedrich Adolph Sorge. 20 June |
| Engels to August Bebel. 21 June |
| Marx to Engels. 22 June |
| Marx to Engels. 24 June |
| Engels to Eduard Bernstein. 26 June |
| Marx to Engels. 4 July |
| Engels to Eduard Bernstein. 15 July |
| Engels to Adolf Hepner. 25 July |
| Engels to Pyotr Lavrov. 31 July |
| Marx to Engels. 3 August |
| Engels to Johann Philipp Becker. 9 August |
| Engels to Eduard Bernstein. 9 August
(abstract) |
| Marx to Engels. 10 August |
| Engels to Friedrich Adolph Sorge. 10 August |
| Engels to Marx. 20 August |
| Engels to Emil Engels Jun. 20 August |
| Marx to Engels. 21 August |
| Marx to Engels. 24 August |
| Engels to Marx. 25 August |
| Engels to Marx. 26 August |
| Engels to Jenny Longuet. 27 August |
| Marx to Engels. 4 September |
| Engels to Marx. 12 September |
| Engels to Karl Kautsky. 12 September |
| Engels to Eduard Bernstein. 13 September |
| Marx to Engels. 16 September |
| Engels to Marx. 18 September |
| Engels to Laura Lafargue. 20 September |
| Engels to Eduard Bernstein. 22 September |
| Engels to August Bebel. 23 September |
| Marx to Engels. 28 September |
| Marx to Engels. 30 September |
| Marx to Laura Lafargue. 9 October |
| Engels to Eduard Bernstein. 20 October |
| Engels to Laura Lafargue. 21 October |
| Engels to Eduard Bernstein. 27 October |
| Engels to August Bebel. 28 October |
| Engels to Paul Lafargue. 30 October |
| Engels to Marx. 1 November |
| Engels to Eduard Bernstein. 3 November |
| Engels to Marx. 3 November |
| Engels to Eduard Bernstein. 4 November |
| Engels to Marx. 6 November |
| Marx to Engels. 8 November |
| Marx to Philipp Stephen King. 9 November |
| Engels to Friedrich Adolph Sorge. 9 November |
| Marx to Eleanor Marx. 10 November |
| Engels to Marx. 11 November |
| Marx to Engels. 11 November |
| Engels to Karl Kautsky. 15 November |
| Marx to Engels. 20 November |
| Engels to Marx. 21 November |
| Marx to Engels. 22 November |
| Engels to Marx. 22 November |
| Engels to Marx. 23 November |
| Marx to Engels. 27 November |
| Engels to Eduard Bernstein. 28 November |
| Engels to Marx. 30 November |
| Marx to Engels. 4 December |
| Marx to Engels. 8 December |
| Engels to Marx. 8 December |
| Engels to Marx. 13 December |
| Engels to Laura Lafargue. 14 December |
| Marx to Laura Lafargue. 14 December |
| Engels to Marx. 15 December |
| Engels to Laura Lafargue. 15 December |
| Engels to Marx. 16 December |
| Engels to Johann Philipp Becker. 16 December |
| Engels to Eduard Bernstein. 16 December |
| Marx to Engels. 18 December |
| Engels to Marx. 19 December |
| Engels to Marx. 22 December |
| Engels to August Bebel. 22 December |
| Marx to Eleanor Marx. 23 December |