Ferdinand Ries is credited as the composer of the Concerto for Two Horns, WoO. 19 preserved in the Berlin State Library. Dated 1811, ostensibly Ries wrote it in the same year as his Horn Sonata, Op. 34, yet the writing for the horns in the Concerto is significantly more demanding. Furthermore, Ries added to the mystery by not claiming the Concerto in his personal catalog of works or mentioning it in any surviving correspondence. The purpose of this dissertation is to study the authorship of the Concerto for Two Horns and offer possible explanations for the variance in horn writing. Biographical information of Ries is given followed by a stylistic analysis of Ries’s known works. A stylistic analysis of the Concerto for Two Horns, WoO. 19 is offered, including a handwriting comparison between the Concerto for Two Horns and Ries’s Horn Sonata. Finally, possible explanations are proposed that rationalize the variance in horn writing between the Concerto for Two Horns, WoO. 19 and Ries’s other compositions that include the horn.