We examined the relationship of crowding to rates of suicides, nonviolent deaths, violent deaths, psychiatric commitments, inmate-on-inmate assaults, disciplinary infractions, and attempted suicides and self-mutilations as evidenced in archival records from four state prison systems. From field research in prisons and jails we obtained data on individual inmates including illness complaints, blood pressure, perceived crowding, and housing evaluations. In general, crowding in prisons appears to be related to increased pathology. In addition, we consider some theoretical issues based on our findings. We have concluded that the primary causes of negative effects related to crowding may be due to cognitive strain, anxiety or fear, and frustration intrinsic to most social interactions in crowded settings. (Author abstract)