Leoš Janáček’s String Quartet No. 1 gives its public the opportunity of speculating about its contents in numerous ways. Janáček marked the title page of its autograph „Z podnětu L. N. Tolstého Kreutzerovy sonáty” [Instigated by L. N. Tolstoy’s Kreutzer Sonata], and, in his letter to Kamila Stösslová, from October 15th, 1924, he noted: ‘I was thinking of a poor woman, tormented, beaten, killed, such as the Russian writer Tolstoy wrote about in his work The Kreutzer Sonata.’ Speculations based on these statements lead musicologists towards a general stressing of the abstract nature of the work. The aim of this article is to show that Janáček’s String Quartet No. 1 is neither programmatic nor purely abstrakt music. To negate the non-musical background of the work is not possible. As a source of inspiration, L. N. Tolstoy’s Kreutzer Sonata is not only the first existing point of research, but, considering Janáček’s printed edition of the novel and its annotations, also a rich source of hidden information. It was not jealousy, as was so often believed, but marital life and the power of music which attracted Janáăek. Apart from the impact of the music, its dramaturgy also concerned him. All the outcome of this research is important; it forms the base for extending the outlines of the creative process, to clarify the relation between the inspiration and the work.