In this master thesis I look at the revivals of Gluck’s Orfeo ed Euridice in London (1770 and 1785), Florence (1771), and Naples (1774). After the premiere of Orfeo ed Euridice in Vienna in 1762, Gluck himself reworked the opera for new productions in Parma (1769) and Paris (1774). The versions studied in my thesis, however, were adapted and included music by other composers, such as Johann Christian Bach and Pietro Alessandro Guglielmi. There were a number of added scenes, new characters, and inserted arias, sometimes in a very contrasting style to what Gluck and Calzabigi tried to achieve in their reform of opera seria. For this reason, the reworkings have often been called pasticcio versions in modern literature.  Through a comparative study of the music manuscripts and the printed libretti, I show that these four productions of the opera exhibit four unique approaches to performing the opera at public opera houses in the late eighteenth century. Orfeo was consistently lengthened in order to make the performance long enough for an evening at the opera, but how it was changed varied considerably according to the context of the performance. This suggests a complexity and nuance of the practice of adaptations and substitutions in late eighteenth-century opera in general, and the reception of Orfeo in particular, that have not previously been fully acknowledged.