The intent of this study is to reveal inmate characteristics that will help identify those inmates likely to commit such offenses so that appropriate preventive precautions can be taken. The study was conducted in several correctional institutions. It first reviewed file information on inmates who committed or were charged with the sexual assault of a female staff member or with a hostage-taking that involved an allegation of sexual assault. Additional information was then obtained from staff members with personal knowledge of the inmate or incident. A total of 13 inmates were identified through this process; however, the number of inmates actually studied was eventually reduced to 11. All of the inmates identified in the study were known sex offenders who had previously sexually assaulted adult women. Most were serving long sentences at the time of the incident studied. These inmates had also committed crimes that had resulted in more physical harm to the victims than is the case with most sex offenders. Many of them had psychiatric histories that involved psychoses, severe personality disorders, or extreme behavioral or mental instability. Previous assaults on female staff and the inmate's most serious past sexual assault are probably the most relevant variables in identifying those inmates who pose the most danger to female staff members. After identifying those inmates at high risk for the sexual assault of female staff, staff should be alerted about such inmates, and the movements of these inmates should be restricted or closely monitored. 6 footnotes