Twenty-six pairs of long-term hospitalized siblings at Middletown (N.Y.) State Hospital were observed and are described. This study is based on personal observations and interviews, collected data from the personnel, and case histories. The division by sex of this sample is 18 groupings of male siblings, two of female, and six pairs of brother and sister. The total ratio of male to female is 45 to 11, which amounts to 80 per cent of male siblings. The diagnostic categories are as follows: 16 groupings of schizophrenics, including one propfschizophrenic; one pair with psychosis with mental deficiency, one senile psychotic and three pairs of brothers from the children's unit, diagnosed primary behavior disturbances. The remaining five pairs each had one schizophrenic member while the others were an epileptic, a mental defective, an alcoholic, a paretic and a senile psychotic. The mean duration of hospitalization for these samples, except the three pairs from the children's unit, is 18 years. Among the 12 groupings of male schizophrenic siblings who have or had sisters, the sisters are reasonably well adjusted in all except one case, and are without any known history of hospitalization for mental illness. Furthermore, all brothers of the two groupings of female siblings were and are considered well adjusted. This observation agrees with findings by Humm in 1932 and recently by Lidz and co-workers. The very heavy incidence of the present sample of 18 pairs of male siblings and only two of female in a hospital population with 55 per cent of females is discussed and a hypothesis offered. A point of interest emerging from the finding is the observation that there exists a different mode of intra-familial relationship, ward behavior, and flow of communication among the 16 pairs of schizophrenic siblings as compared to the non-schizophrenics. The data and observations seem to indicate that the lack of interpersonal relations among long-term hospitalized siblings, especially schizophrenics, could be enforced and shaped by institutional processes but basically it is part and parcel of the social crippling due to schizophrenia.