(Received 1 December 2006; accepted 8 September 2007)

The author analyses the concept of mental pain, which as Seelenschmerz had already been described in the works of Freud, and systematizes the theoretical and clinical contributions of Bion to the issue of mental pain. Various developments of the concept are examined throughout Bion's work, as well as the different links that he established between mental pain and different theories on frustration, thought, psychic transformations, and the early infant-mother relationship. Conceptual links between different theoretical models are proposed, and clinical data are presented with implications for clinical work. How to conceptualize and deal in clinical practice with unnameable and unthinkable mental pains—emotions without a name—is one of the issues the author aims to answer in this article.