Homicides increased from 65 per month in 1965 to almost 75 per month in 1974. A brief decline in 1975 and 1976 was followed by increases from 1977 to 1981. A companion study showed that homicide is actually many different crimes, with varying characteristics of victims, offenders, and circumstances. This complexity also appears in the analyses of homicide changes over time. The most common type of homicide in Chicago is male on male, and the rapid increase in homicide in the late 1970's occurred only in this type of homicide. The rising homicide rates of the late 1960's and early 1970's were mainly robbery and assault homicides, both of which peaked in 1974 and decreased in the mid-1970's. Homicides involving black victims or offenders generally decreased from 1977 to 1981, whereas almost every kind of homicide involving Hispanic victims or offenders increased during the same period. Homicide committed without a firearm changed little over the 17 years. The increases and decreases occurred in homicides committed with firearms. Robbery homicides committed by young black males increased in the early part of the 17 years and then decreased, possibly in response to a societal change as yet unidentified. Figures, tables, summary of characteristics of homicides, notes, and 155 references.