This chapter explores the ebbs and flows of Emil Kraepelin’s influence over Soviet psychiatry during the Stalin era. Kraepelin’s conception of mental illnesses as ‘natural disease entities’ held considerable appeal for Soviet psychiatrists who foregrounded the role of endogenous factors in mental illness, as well as those who sought to apply Pavlov’s theories of ‘higher nervous activity’ to the psychiatric clinic. Due to the social orientation of Soviet psychiatry in the 1920s and early 1930s, as well as to the lingering legacy of psychoanalysis, however, ‘Kraepelinism’ encountered considerable resistance. Soviet psychiatrists continued to be critical of biological framings of mental illness throughout the Stalin era.