Using a data set for St. Louis, this article documents a substantial decline in intimate partner homicide over the past 25 years, compares intimate partner events with other types of homicide, and explores the relationship between changes over time in the level and type of intimate partner homicide and the living arrangements of men and women. Much of the decrease in partner homicide is a function of the declining rate of marriage; in certain key respects, homicides involving unmarried couples more closely resemble acquaintance homicides than spousal homicides. Findings raise the question of the displacement of victims and offenders, particularly females, to other victim-offender categories in homicide. The article also suggests that some of the broad social changes involving marriage and family that have contributed to the decline in intimate partner homicide may be deeply implicated in the dramatic rise in youth violence over the past 10 years. Tables, notes, references