Alexander Grechaninov was one of the most important composers of the late Russian Romantic School. By the second half of the twentieth century he remained one of the few living composers who continued the traditions of the great Russian Romantic masters, such as Tchaikovsky and Rimsky-Korsakov. He is primarily known for his liturgical works, which are truly masterpieces of this genre. Because many of his instrumental works remain unpublished, particularly the chamber works, they continue to be undeservedly ignored in the concert hall. Grechaninov's unpublished works for clarinet include Septet for Clarinet, Bassoon and String Quintet, Op. 172a, Serenade for Clarinet and String Orchestra (without opus number), and Sonata No. 1 for Clarinet and Piano, Op. 161. This project not only brings to light Grechaninov's unpublished clarinet works, but also emphasizes the importance of his published clarinet pieces which have to date been forgotten, especially in the United States. The writer prepares a performance edition of the Sonata No. 1, Op.161 from Grechaninov's original autograph manuscript which is held in the New York Public Library's Toscanini Archives. After a brief introduction, the document describes Grechaninov's biography, including his historical and societal background, compositional growth throughout his career, and outside influences to which he would have been exposed (Chapter 2). Chapter 3 discusses in details Grechaninov's compositional output and distinct features of his style. Chapters 4 and 5 discuss the published and unpublished works for clarinet by Grechaninov. Chapter 6 provides a detailed structural and tonal analysis of the Sonata No. 1, Op. 161 and discusses the process of editing. Included in the appendices are: performance edition of the Sonata No. 1 for Clarinet and Piano, Op. 161 (score and clarinet part); photocopy of the original autograph manuscript of the Sonata No. 1 for Clarinet and Piano, Op. 161 (score and viola part); photocopy of the original autograph manuscript of the Septet for Clarinet, Bassoon and String Quintet, Op. 172a; and photocopy of the original autograph manuscript of the Serenade for Clarinet and String Orchestra, without opus number.