These 35 situations involved 62 attacks in which 59 officers were assaulted by 39 assailants. Nearly 160 variables associated with ambush attacks were examined in the general areas of victim, assailant, and environmental characteristics; dynamics of the incident; and risk-reduction techniques and countermeasures. While the ambushes studied often were very brief in duration, they were very dangerous, with approximately one in six officers being killed during the attack. Further, they were unusual in being both violent and planned. In 36.8 percent of the cases, the victim was known to the assailant. Most of the assailants who were apprehended were members of lower socioeconomic groups and shared the characteristics of a subculture of violence. Of 15 assailants, 11 had extensive criminal histories. Ambushes tended to be concentrated in urban areas and to be more prevalent during the winter. Victims were usually male, white, patrolmen with 5 or fewer years police experience. Most officers were engaged in routine or passive behaviors prior to the ambush, with little interaction between the offender and victim. Differences between ambush assaults and general police assaults are delineated. Index and 41 references.