The purpose of this article is to critically review and synthesize the literature related to the general concepts and the process of diagnosing the client's condition, and the possible variables which influence diagnostic practise in nursing. It is suggested that statistical theories are capable of capturing the diagnostic process and offer an effective means to predict diagnostic decisions. Studies underpinned by information-processing theory argue that diagnosing a patient's condition follows a hypothetico-deductive model that consists of specific stages. Those who hold a phenomenological perspective remark that there is yet another form of diagnostic practise: intuitive reasoning, which plays an important role in diagnosing the patient's clinical condition. Other related studies suggest that diagnostic practise is contingent on some personal, psychosocial, and structural variables. Regrettably, these studies offer no conclusive explanation to delineate diagnostic practise in nursing. Based on the literature reviewed, a conceptual framework is suggested to help articulate the underlying structures and processes of diagnostic practise in nursing.