Evidence of work clearly connected to the composition of the Eroica is traceable from 1802 onwards. This consist of letters, sketches and other materials in the composer’s hand but also by copyists and collaborators, who worked with him. Although some fundamental documents ‘such as the autograph score’ are now lost, these materials make it possible to reconstruct in detail many aspects of the genesis of the symphony. This chapter seeks to reconstruct the different stages in the genesis of the Eroica, on the basis of a well-established research tradition ‘represented by scholar such as Gustav Nottebohm, Alan Tyson, Otto Biba, Michael C. Tusa, Bathia Churgin and Lewis Lockwood’. It focuses on general aspects of Beethoven’s creative process and draw attention to the variety of possible methodological approaches developed by musicologists during nearly two centuries of research on the subject.