Of 94 assaults at the Federal facility, 40 were serious (involving pain and discomfort), and 54 were minor (not involving physical harm, e.g., shoving, pushing). In the State facility, 18 of 57 were minor, and 39 were serious. In both facilities, the majority of minor and serious assaults against staff occurred in high security units, although assaults in the State facility tended to be more evenly distributed among the various housing units. The lowest percentage of assaults occurred during the morning shift, while the highest were in the day shift (8 am to 4 pm), probably because staff-inmate interactions are most frequent during this period. Assaults did not vary substantially with officer age or sex, but did vary when the number of years of work experience were considered. Officers who had worked less than 1 year were more likely to be assaulted than those with more experience. In the Federal facility, 3 percent of assaults occurred when officers intervened in fights; while 32 percent of assaults occurred in this situation in the State facility. In both facilities, assaults generally occurred without much warning or verbal exchange. Finally, the majority of minor assaults occurred when the officer was alone, while the majority of serious assaults occurred when other staff members were present. 6 tables and 10 references.