Prisons selected for the study were Dade (DCI) and Union Correctional Institutions (UCI), Florida State Prison (FSP), and Tallahassee Federal Correctional Institution. These two medium and two maximum security prisons are different structurally and architecturally. A violent-environment questionnaire was developed and administered to 392 inmates, and data were collected on 1,329 assaults during 1979-80 in the 4 prisons. The study focuses on two components that lead to the perception of crowding: spacial density -- the amount of space per person; and social density -- the number of people encountered over time. At each of the four institutions, the rate of assault appeared to have no sympathetic or reactionary response to the size of the monthly population. In UCI and FSP, high security institutions that house troublemakers from other institutions, as assaults increased the percentage of inmates in disciplinary confinement increased and assaults dropped sharply. The amount of space per person acted independently of the rate of assault. Of the inmate respondents, 75 percent believed their prison was crowded, and 73 percent believed their dining area was crowded. DCI, a new facility with an open campus-like atmosphere, scored highest in ratings of sleeping and bathroom privacy. Over three-fourths of all inmates felt their visiting areas allowed no privacy and two-thirds felt their visiting area was crowded. The failure to find reduced reports of assault among the less crowded residents runs counter to previous research findings. Tables, graphs, footnotes, and 18 references are included.