Rates of criminal homicide have been increasing in many ma jor metropolitan areas. In Chicago from 1965 to 1970; the rate of homicides noted by the police more than doubled. A study of Patterns of homicide during that period reveals that robbey -killings, killings involving younger victims and offenders, group- related killings, and gun killings all increased far more substan tially than aggregate homicide rates. Homicide offense rates for black males aged 15-24 almost tripled during the six years, while victimization among the same group more than tripled. The dramatic increase in robbery killings appeared to be but one manifestation of a broader increase in young, group-related, gun homicides.