There are two violin concertos in Béla Bartók’s body of compositions. The first concerto written in 1907 is obscure and rarely heard, while the second, completed in 1939, is widely performed and generally regarded as a twentieth-century masterwork. Bartók had contrasting relationships with the violinists for whom the works were written: the first, for Stefi Geyer; and the second, for Zoltán Székely. My thesis will compare the two concerti, illustrating how the second refines, expands and more fully develops the compositional approach of the first, as well as the working relationship and influence the performers had on the ultimate outcome of the concerti. This comparison of two works with very different outcomes offers insights into Bartók’s compositional methods and development.