| Engels to Friedrich Adolph Sorge. 3 January |
| Engels to Karl Kautsky. 7 January |
| Engels to Pasquale Martignetti. 9 January |
| Engels to Stanislaw Mendelson. 13 January |
| Engels to Karl Kautsky. 15 January |
| Engels to Friedrich Adolph Sorge. 17 January |
| Engels to Stanislaw Mendelson. 18 January |
| Engels to Carl Schorlemmer. 27 January |
| Engels to Heinrich Scheu. 27 January |
| Engels to Hermann Schlüter. 29 January |
| Engels to Paul Lafargue. 31 January |
| Engels to Karl Kautsky. 3 February |
| Engels to Laura Lafargue. 5 February |
| Engels to Paul Lafargue. 6 February |
| Engels to Paul Lafargue. 10 February |
| Engels to Friedrich Adolph Sorge. 11 February |
| Engels to Karl Kautsky. 11 February |
| Engels to Karl Kautsky. 21 February |
| Engels to Karl Kautsky. 23 February |
| Engels to Karl Kautsky. 23 February |
| Engels to Antonio Labriola. 27 February |
| Engels to Friedrich Adolph Sorge. 4 March |
| Engels to Paul Lafargue. 6 March |
| Engels to Henri Ravé. 6 March |
| Engels to Pasquale Martignetti. 6 March |
| Engels to Filippo Turati. 7 March |
| Engels to Henri Ravé. Mid-March |
| Engels to Karl Kautsky. 17 March |
| Engels to Friedrich Adolph Sorge. 21 March |
| Engels to Hermann Schlüter. 21 March |
| Engels to Max Oppenheim. 24 March |
| Engels to Laura Lafargue. 30 March |
| Engels to Stanislaw Mendelson. 31 March |
| Engels to August Bebel. c. 1 April |
| Engels to Karl Kautsky. 2 April |
| Engels to Pasquale Martignetti. 2 April |
| Engels to Romualdo Fantuzzi. 2 April |
| Engels to Paul Lafargue. 3 April |
| Engels to Karl Kautsky. 7 April |
| Engels to Henri Ravé. 7 April |
| Engels to Friedrich Adolph Sorge. 8 April |
| Engels to Walery Wróblewski. 9 April |
| Engels to Heinrich Scheu. 10 April |
| Engels to Leo Frankel. 24 April |
| Engels to Karl Kautsky. 30 April |
| Engels to August Bebel. 1-2 May |
| Engels to Laura Lafargue. 4 May |
| Engels to Paul Lafargue. 19 May |
| Engels to Paul Lafargue. 29 May |
| Engels to Franz Mehring. 5 June |
| Engels to Friedrich Adolph Sorge. 10 June |
| Engels to Karl Kautsky. 13 June |
| Engels to Laura Lafargue. 13 June |
| Engels to Karl Kautsky. 16 June |
| Engels to Pasquale Martignetti. 19 June |
| Engels to Victor Adler. 26 June |
| Engels to Paul Lafargue. 28 June |
| Engels to Karl Kautsky. 29 June |
| Engels to Conrad Schmidt. 1 July |
| Engels to Laura Lafargue. 7 July |
| Engels to Johann Gustav Vogt. 8 July |
| Engels to Laura Lafargue. 12 July |
| Engels to Laura Lafargue. 20 July |
| Engels to Victor Adler. 22 July |
| Engels to Emma Adler. 22 July |
| Engels to Friedrich Adolph Sorge. 9-11 August |
| Engels to Laura Lafargue. 17 August |
| Engels to Nikolai Danielson. 2 September |
| Engels to Friedrich Adolph Sorge. 2 September |
| Engels to Paul Lafargue. 2 September |
| Engels to Friedrich Adolph Sorge. 14 September |
| Engels to Karl Kautsky. 28 September |
| Engels to August Bebel. 29 Sep/1 Oct |
| Engels to Friedrich Adolph Sorge. 30 September |
| Engels to Laura Lafargue. 2 October |
| Engels to August Bebel. 6 October |
| Engels to Paul Lafargue. 13 October |
| Engels to August Bebel. 13 October |
| Engels to Laura Lafargue. 13 October |
| Engels to Karl Kautsky. 14 October |
| Engels to Laura Lafargue. 22 October |
| Engels to Friedrich Adolph Sorge. 24 October |
| Engels to August Bebel. 24/26 October |
| Engels to Karl Kautsky. 25-26 October |
| Engels to Laura Lafargue. 27 October |
| Engels to Friedrich Adolph Sorge. 29 October |
| Engels to Nikolai Danielson. 29-31 October |
| Engels to Paul Lafargue. 31 October |
| Engels to Conrad Schmidt. 1 November |
| Engels to Laura Lafargue. 9 November |
| Engels to August Bebel. 10 November |
| Engels to Oscar Heidfeld. 12 November |
| Engels to Friedrich Adolph Sorge. 14 November |
| Engels to Friedrich Adolph Sorge. 21 November |
| Engels to August Bebel. 25 November |
| Engels to Laura Lafargue. 27 November |
| Engels to August Bebel. 1 December |
| Engels to Laura Lafargue. 1 December |
| Engels to Natalie Liebknecht. 2 December |
| Engels to Karl Kautsky. 3 December |
| Engels to Paul Lafargue. 3 December |
| Engels to Laura Lafargue. 19 December |
| Engels to Eduard Bernstein. 23 December |
| Engels to Karl Kautsky. 27 December |
| Engels to Anna and Hermann Schlüter. 30 December |