Sleževičius was an avid theater lover. Already in Odessa he established a cultural society "Rūta" which was one of the centers of Lithuanian cultural life in the city. After returning to Lithuania, Sleževičius took part in establishing a cultural society of the same name in Vilnius, acting as its secretary. The society was active between 1908 and 1918 and operated a library, organized lectures and concerts, and staged over 50 plays. Sleževičius directed several of the them, with his staging of Juliusz Słowacki's "Mindaugas" (1908) and Vincas Nagornockis' "Živilė" (1909) particularly well received.