The subjects were 13,000 males and females born in 1958 who lived in Philadelphia from ages 10 through 17 and had at least one police contact by age 18. The analysis considered eight categories of offenses: criminal homicide, forcible robbery, aggravated assault, burglary, larceny, vehicle theft, and simple assault. The spatial relationships among the offense and the residences were compared for each offense. In almost half the cases, the offender, the victim, and the offense site were located in different census tracts, indicating high spatial mobility. Low spatial mobility was more likely to occur in offenses against persons than in offenses against property, confirming other research findings. A review of literature on mobility triangles, data tables, and 13 reference notes.