This paper explores the therapeutic value of considering psychoanalytic diagnoses as co-constructions, and emphasizes two interrelated points: First, there are distinctions between medical, psychiatric, and psychoanalytic diagnoses, and similarly, a distinction may be drawn between diagnoses as nouns and the activity of diagnosing. Second, the author stresses that psychoanalytic diagnoses are theory bound. Various competing theories facilitate or interfere with the maintenance of an optimal analytic attitude. Some theories facilitate an analyst's urge to engage in the activity of diagnosing, which may reflect a destructive countertransference enactment. Analytic data in support of these premises is presented and discussed.