Perverse thinking is found not only in perversion, but also in other psychic structures. It is bound neither to aggressive nor to sexual experience. It is a state of mental functioning outside reality and fantasy, and occurs whenever an individual gets into an existential irritation, which demands a fundamental change. It creates denial as a protection against destruction that does not really change reality, but creates another reality besides the objective one. It is thinking in terms of two incompatible realities and the replacement of the knowledge of its incompatibility by the idea of its being normal: the acceptance of the coexistence of two states of thinking that are excluding one another is the perversion of normality. By the use of some case material, this paper demonstrates how this mode of functioning can intrude into transference-countertransference dynamics, and how one can try to handle it.