Two separate samples of Federal inmates were used to obtain baseline data for inmate violent behavior. Misconduct was measured by information from incident reports for each inmate. For both samples, the base rate of involvement in violent activity was 7 percent. In the absence of any other information about an inmate's tendency toward violence, the chance that he will become involved in such behavior are about 7 in 100. Actuarial data, such as information about social background and criminal history, can complement base rate information and enhance the accuracy of prediction. Actuarial variables such as race, education, or unemployment do not explain the use of violence, but they help to 'predict' it since they are categorical standards for the complex subcultural experiences which condition a person to use violence in a variety of situations. Variables which suggest a connection between certain background data and violent behavior can be used to make custody classifications. Experts have also recommended attention to environmental variables in enhancing accuracy in predicting violence. Family, peer, and work environments, as well as the availability of weapons, victims, and alcohol are important. Research should focus particularly on situational variables in prisons that correlate with violent behavior, so that correctional staff can help prevent or be prepared to counter violence in such situations. Tabular data are provided.