The study focused on 83 assault events which produced 143 assaults on police. A total of 109 officers were assaulted by 125 suspects. There were 42 single and 41 multiple assault events. The incidents occurred throughout the United States from September 1972 through August 1973. The research design used 163 variables for each assault incident, with variables divided into categories that described (1) the environmental characteristics of the incident, (2) the characteristics of the assaulted officer, (3) assailant characteristics, and (4) the dynamics of the assault incident. Prior studies bearing upon the study subject indicate that police assaults, robbery, and violence all seem to be concentrated among young males in lower socioeconomic groups. Nonwhites are overrepresented in each category, but race does not seem to be the deciding factor. Police assaults apparently resemble violent crime more than robbery, but no firm conclusions are possible at this point. Data from the current study indicate robbery and assaults on police during robbery share similar environmental characteristics. They are predominantly urban, occur more often in winter months, during the latter half of the week, and at night. Robbery-related police assaults differ substantially from general police assaults by the environmental characteristics of location, season, and time of day. Tabular data and 51 references are provided.