Homicide is not one crime but many. Most (69 percent) of the homicides began as brawls or arguments, 17 percent as robberies, 1 percent as rapes or burglaries, and 1 percent in some other way. Differing types of homicides (e.g. assault, robbery, rape homicide) are more common among some ethnic and age groups than others. Some homicides are more a function of victim vulnerability, while others are more a function of offender characteristics. Over the 17 years, the number of homicides changed tremendously: rates increased rapidly in the 1960's through 1974, declined in 1975 and 1976, and again increased from 1977 to 1981. Despite differing population patterns, whatever caused the rapid increase in the late 1960's had an effect on every race and ethnic group and involved all types of homicides. The increase in 1970 was especially apparent in gang-related homicides and black-on-black firearm assault homicides. Patterns in the 1970's were more complex: many types of homicides remained stable, gang and black-on-black homicides decreased, and robbery homicides (particularly of black and Hispanic victims) increased. 45 figures, 29 tables, 16 notes, and 154 references. (Author summary modified)