The author approaches the question of translation from the angle of the specific clinical field of extreme clinical situations, and in particular patients suffering from mental deficiency. Confronted with altered language that is not in keeping with the “normal” linguistic model, or even with the absence of verbal language, the psychoanalyst finds himself in the position of a translator. But rather than translation from one language to another, it is matter of transformation, in W. R. Bion’s sense, not between two constituted languages, but between two registers of heterogeneous mental functioning, the sensory and the verbal. This idea is illustrated by two clinical cases which the author describes as untranslatable, since their strangeness undermines the therapist’s rational capacities for understanding, requiring him to engage in a destabilizing logic where he has recourse to a very free mode of associativity and artistic references.