|
| Marx to Eduard von Muller-Tellering. 12 March |
| Marx to Engels. 19 November |
| Marx to Engels. 23 November |
|
| Marx to Engels. 7 January |
| Engels to Marx. 8 January |
| Engels to Marx. 29 January |
| Marx to Engels. 3 February |
Engels to Marx. 5 February
|
| Marx to Engels. 10 February |
| Marx to Engels. 11 February |
| Engels to Marx. 13 February |
| Marx to Engels. 23 February |
| Marx to Engels. 31 March |
| Marx to Engels. 2 April |
| Engels to Marx. 3 April |
| Engels to Marx. 23 May |
| Marx to Engels. 16 June |
| Engels to Joseph Weydemeyer. 19 June |
| Marx to Joseph Weydemeyer. 27 June |
| Engels to Ernst Dronke. 9 July |
| Marx to Engels. 13 July |
| Engels to Marx. 17 July 1851 |
| Engels to Marx. c. 20 July 1851 |
| Marx to Engels. 8 August |
| Engels to Marx. c. 11 August |
| Marx to Engels. 14 August |
| Marx to Engels. 13 September 1851 |
| Marx to Engels. 23 September |
| Engels to Marx. 23 September |
| Engels to Marx. 26 September |
| Marx to Engels. 13 October |
| Marx to Joseph Weydemeyer. 16 October |
| Marx to Engels. 24 November |
| Engels to Marx. 3 December |
| Engels to Marx. 11 December 1851 |
| Marx to Ferdinand Freiligrath. 27 December |
|
| Marx to Joseph Weydemeyer. 16 January |
| Marx to Engels. 24 January |
| Engels to Marx. 28 January |
| Engels to Marx. 29 January |
| Marx to Joseph Weydemeyer. 30 January |
| Engels to Joseph Weydemeyer. 30 January |
| Marx to Engels. 18 February |
| Marx to Joseph Weydemeyer. 5 March |
| Engels to Marx. 18 March |
| Engels to Marx. 29 April |
| Engels to Marx. 7 May |
| Marx to Adolf Cluss. 7 and about 15 May |
| Marx to Jenny Marx. 11 June |
| Marx to Adolf Cluss. 20 July |
| Engels to Marx. 24 August |
| Marx to Engels. 2 September |
| Engels to Marx. 23 September |
| Marx to Engels. 23 September |
| Engels to Marx. Sep 24 1852 |
| Engels to Marx. 4 October |
| Marx to Adolf Cluss. 5 October |
| Marx to Adolf Cluss. 8 October |
| Marx to Adolf Cluss. 7 December |
| Marx to Adolf Cluss. 14 December |
|
| Engels to Marx. 11 February |
| Marx to Engels. 23 February |
| Engels to Marx. 11 March |
| Marx to Adolf Cluss. 25 March |
| Engels to Joseph Weydemeyer. 12 April |
| Marx to Adolf Cluss. 17 April |
| Engels to Marx. Before 28 May |
| Marx to Engels. 2 June |
| Engels to Marx. 6 June |
| Marx to Engels. 14 June |
| Marx to Adolf Cluss. c. 14 June |
| Marx to Engels. 7 September |
| Marx to Adolf Cluss. 15 September |
| Marx to Engels. 30 September |
| Marx to Adolf Cluss. 5 October |
| Marx to Adolf Cluss. 18 October |
| Marx to Adolf Cluss. Mid-November |
| Marx to Engels. 23 November |
| Marx to Engels. 14 December |
|
| Marx to Engels. 25 January |
| Engels to H. J. Lincoln, Editor of The Daily News. 30 March |
| Engels to Marx. 20 April |
| Engels to Marx. 21 April |
| Marx to Engels. 22 April |
| Marx to Engels. 3 May |
| Marx to Engels. 21 June |
| Marx to Engels. 27 July |
| Marx to Engels. 2 September |
| Marx to Engels. 13 September |
| Marx to Engels. 17 October |
| Marx to Engels. 26 October |
|
| Marx to Ferdinand Lassalle. 23 January |
| Marx to Engels. 2 February |
| Marx to Engels. 13 February |
| Marx to Engels. 8 March |
| Marx to Engels. 16 March |
| Marx to Engels. 27 March |
| Marx to Engels. 30 March |
| Marx to Engels. 6 April |
| Marx to Engels. 12 April |
| Marx to Engels. 18 May |
| Marx to Engels. 6 September |
| Marx to Amalie Daniels. 6 September |
| Marx to Ferdinand Lassalle. 8 November |
| Marx to Engels. 14 December |
|
| Engels to Marx. 7 February |
| Marx to Engels. 5 March |
| Marx to Engels. 16 April |
| Engels to Marx. 23 May |
| Marx to Jenny Marx. 21 June |
| Marx to Jenny Marx. 8 August |
| Marx to Engels. 26 September |
| Engels to Marx. After 26 Sept. |
| Marx to Engels. 30 October 1856 |
| Engels to Marx. 17 November |
| Marx to Engels. 2 December |
|
| Marx to Engels. 24 March |
| Marx to Engels. 31 March |
| Engels to Marx. 22 April |
| Marx to Engels. 22 May |
| Marx to Engels. 6 July |
| Marx to Engels. 14 July |
| Marx to Engels. 15 August |
| Marx to Engels. 21 September |
| Marx to Engels. 23 September |
| Engels to Marx. 24 September |
| Marx to Engels. 25 September |
| Engels to Marx. 29 October |
| Marx to Engels. 31 October |
| Marx to Engels. 13 November |
| Marx to Engels. 24 November |
| Marx to Engels. 8 December |
| Marx to Conrad Schramm. 8 December |
| Marx to Engels. 18 December |
| Marx to Ferdinand Lassalle. 21 December |
| Marx to Engels. 22 December |
| Marx to Engels. 25 December |
|
| Engels to Marx. 7 January |
| Marx to Engels. 11 January |
| Engels to Marx. 14 January |
| Marx to Engels. 16 January |
| Marx to Engels. 1 February |
| Marx to Ferdinand Lassalle. 22 February |
| Marx to Engels. 22 February |
| Marx to Engels. 2 March |
| Engels to Marx. 4 March |
| Marx to Engels. 5 March |
| Engels to Marx. 17 March |
| Marx to Engels. 2 April |
| Engels to Marx. 9 April |
| Engels to Jenny Marx. 11 May |
| Engels to Jenny and Laura Marx. 11 May |
| Marx to Ferdinand Lassalle. 31 May |
| Marx to Engels. 31 May |
| Marx to Ferdinand Lassalle. 10 June |
| Engels to Marx. 14 July |
| Marx to Engels. 15 July |
| Marx to Engels. 13 August |
| Engels to Marx. 7 October |
| Marx to Engels. 8 October |
| Marx to Ferdinand Lassalle. 12 November |
|
| Marx to Engels 13/15 January |
| Marx to Joseph Weydemeyer 1 February |
| Marx to Ferdinand Lassalle 2 February |
| Marx to Engels 2 February |
| Marx to Ferdinand Lassalle 4 February |
| Marx to Engels 8 February |
| Marx to Engels 9 February |
| Marx to Engels 22 February |
| Marx to Ferdinand Lassalle 25 February |
| Marx to Engels 25 February |
| Marx to Engels 25 February |
| Marx to Ferdinand Lassalle 28 March |
| Marx to Ferdinand Lassalle 19 April |
| Marx to Ferdinand Lassalle 5 May |
| Marx to Engels 6 May |
| Marx to Max Friedlander 16 May |
| Marx to Engels 18 May |
| Engels to Ferdinand Lassalle 18 May |
| Marx to Engels 10 June |
| Marx to Engels 22 July |
| Marx to Ferdinand Lassalle. Not before 2 October |
| Marx to Ferdinand Lassalle 6 November |
| Marx to Engels 26 November |
| Engels to Marx 28 November |
| Marx to Engels 10 December |
| Engels to Marx 11/12 Dec. |
| Marx to Engels 13 December |
| Engels to Jenny Marx 22 Dec. |