I examine Richard Dedekind's important contributions to set theory. These contributions are made in his mathematical work and I present an exposition of several of his mathematical papers. I develop my paper in the following sections:
1. Dedekind's first contacts with the concept of set [1855-1858]
2. The manuscript of 1858 and the paper of 1872
3. «Supplement X» of Dirichlet's Lectures on Number Theory, second edition 
4. The text of 1888 and the manuscript of 1872-1878
5. An unpublished manuscript of 1887-1897: the dangers of set theory
6. The unpulished manuscripts of 1887 and 1889
7. Dedekind and topology
and I show that Dedekind's contributions to set theory are very important and that without them possibly the introduction of set theory into mathematicical work might have appeared later that it did.
"Dedekind y la teoría de conjuntos [Dedekind and the theory of sets]." Mod. Log. 3 (3) 215 - 305, June 1993.