SUMMARY The incidence of reduplicative paramnesia was sampled with a structured interview in 50 consecutive alcoholic inpatients. Four had reduplicative paramnesia (RP group) and 46 did not (non-RP group). Three of four patients in RP group had acute right hemispheric lesions and none had a left hemispheric lesion; 19 non-RP patients had left hemispheric lesions, 2 had right, and 25 had none. These data are in keeping with the previous suggestions that the neuroanatomical basis for reduplicative paramnesia is an acute right hemispheric lesion superimposed on chronic diffuse or bifrontal deficit.Reduplicative paramnesia' is a specific disturbance in memory characterised by subjective certainty that a familiar place, person, object or body part has been duplicated. It is most commonly seen in postraumatic encephalopathy,2 although it has been described in other conditions as well, such as tumours of the third ventricle and upper brainstem, rupture of aneurysms of the circle of Willis and arteriovenous malformations, prefrontal lobotomy, after electroconvulsive therapy and other metabolic and toxic encephalopathies.2 3 It has been suggested that it is a result of a combination of right hemispheric and frontal-lobe pathology.4-1 l These suggestions, however, emanate from analyses of single case studies or selected cases. To provide a better estimate of neuropathological correlates of reduplicative paramnesia, we administered a structured interview designed to elicit paramnesic phenomena to 50 consecutive patients who met the study's criteria. Based on past experience in this centre, the following criteria for patients' selection were adopted to increase the probability of discovering patients with reduplicative paramnesia. The patients were (1) at risk for diffuse cortical or bifrontal dysfunction secondary to alcoholism and (2) had an acute neurological event necessitating the admission. Accepted 10 February 1988 were studied. All were males (age 30-76 years). None had an acute confusional state when studied. The structured questionnaire given to elicit reduplicative paramnesia is given in table 1. This questionnaire covered the possibilities of reduplicative paramnesia for place, person and body parts. It was initially administered by a neurology resident (HH) and the presence of reduplicative paramnesia was later verified independently by a board-certified neurologist (NPV) and a licensed neuropsychologist (MFG). The reduplicative paramnesia was rated as present only if the belief persisted for a week or more despite counter-argument. The clinical characteristics of the two groups were compiled in detail using both direct patient interviews and their clinical records. Three of the patients with reduplicative paramnesia were followed up to a period of one year jointly by the neurology resident and the staff neurologist. Subjects and methodsThe relative frequency of presence or absence of right hemispheric lesions in the two groups was tested with chisquare test for independence with Yate's correction.