The research focused on basic trends in each of the features of the targeted homicides (e.g., gang, drug, youthful offenders, youthful victims, and guns) to determine whether this type of homicides had particularly strong spatial and temporal patterns. The research then used a fixed-effects logit model to study the neighborhood-level persistence of homicide events. Results were consistent with expectations in that drug and gang homicides displayed substantial concentrations of violent incidents spatially and temporally within different neighborhoods in a city. Findings also indicated localized temporal dependencies, in which a recent homicide changed the probability of another homicide in the same local area. Both drug and gang homicides displayed indications of self-limiting suppression effects that inhibited extended periods of sustained high rates of these types of violence in the same area. Finally, data indicated cross-type diffusion from drug and gang homicides to subsequently higher rates of other gun homicides involving young offenders or victims. Figures, tables, note, and 18 references (Author abstract modified)