[Translation of the prologue to the Libro de medicamentos simples by Abû-l-Salt of Denia].

This article offers the Spanish translation of the theoretical introduction that Abu-l-Salt of Denia (1068-1134) placed at the beginning of his treatise on simple drugs. In his introduction he explained the reasons for preparing compound drugs, and how to prepare them. Although the rest of the book was translated from Arabic into Latin by Arnau de Vilanova (c. 1283) this introduction is not found in any of the extant Latin manuscripts and therefore does not appear in the critical edition of the works of Arnau.