Despite significant decreases in violent-crime rates for both adults and juveniles in recent years, homicide is the second leading cause of death for juveniles. In an effort to identify influential factors related to homicide rates among juveniles, the current study focused on structural measures based in the tradition of social disorganization theory. The study addressed the influence of family poverty, labor market structures, family disruption, and other structural correlates on juvenile-specific homicide rates and their change over time. The units of analysis were 159 U.S. cities with populations greater than 100,000 in 1980 and 1990, and for which complete census and homicide data were available. The dependent variable was the number of youth-on-youth homicides in each city. Homicide data were obtained from the FBI's Supplementary Homicide Reports. The total number of juvenile homicides were calculated over two separate 5-year periods (1980-84 and 1990-94). The independent variables pertained to family-specific and urban-related measures of social and economic disadvantage. To control for the population at risk, the number of persons between 5 and 17 years old in each city was calculated. To assess the influence of the predictor variables on youth-on-youth homicide, separate cross-sectional negative binomial regression models for the 1980-84 and 1990-94 youth-on-youth homicide counts were estimated. The findings indicate that concentrated disadvantage was associated with youth-on-youth homicide rates in the cities over time. Apparently, the growth in concentrated disadvantage and divorce across large U.S. cities was responsible for a significant proportion of the increase in the incidence in which juveniles killed one another. The authors suggest that measures to counter juvenile homicide should focus on broad-scale structural transformations in urban communities that will reduce poverty and social disorganization. 3 tables, 1 figure, appended supplementary data, and 65 references