Much has changed in clinical practice and theory that bears on the diagnosis and treatment of perversion since Freud's Three Essays on the Theory of Sexuality (1905). Definitions of perversion have been freed from assumptions of a heterosexual normality and from moralistic interpretations. The authors endorse the current emphasis on aggression and early narcissistic problems and include the notion of splitting and sexualized scenarios in their definition of perversion. They present several vignettes of male and female patients to demonstrate the debts owed to Freud's theories and the way in which their thinking differs. They emphasize the understanding of the transference-countertransference picture and the patient's management and control of excitement.