In this paper we will present a case history of a pair of schizophrenic identical twins. In doing so we have two purposes in mind. First, we will make observations specific to our patients, emphasizing the relationship between their nonpsychotic and psychotic behavior as twins. Secondly, we suggest that study of material from the psychotic episodes of schizophrenic twins can be used as an additional tool to understand twins in general. The presentation consists of the common childhood and family history, the individual histories, and reports of psychological testing. In addition, in tabular form, we have summarized the data dealing with the acceptance and rejection of the twin relationship by each twin in both psychotic and nonpsychotic periods. In the commentary, we will emphasize the psychodynamic significance of this latter material. Report of Cases Case Material.—The twins, 43-year-old women, were admitted to