The purpose of this study is to thoroughly analyze and to create a performance guide of the multi-movement guitar sonatas by Fernando Sor and Mauro Giulian. The works include Sonatas, Opp. 22 and 25 by Sor, and Sonata, Op. 15 by Giuliani. Although the composers are well known to the guitar community, the number of detailed studies of these works is still limited. The present essay is a result of the desire to study them. It contains a short history of the origin of the six-string guitar, the biographies of Sor and Giuliani, and also a brief review of selected writings on sonata form that will help the reader understand the musical form better. The main portion of this study consists of detailed analyses and a performance guide to the sonatas. Theoretical, technical, and stylistic issues are addressed in depth.