The Uniform Crime Report provided a sufficiently large and geographically diverse data set to make certain assumptions about the nature of crime committed by juveniles under 12 years of age. Males constituted the majority of under 12 offenders, and most were 10 or 11 years of age. Most of the physical assaults committed by under 12 offenders involved common assaults; more serious or aggravated assaults that caused physical damage or required hospitalization were minimal. About 62 percent of under 12 mischief occurred in homes, parking lots, streets, and roads. Neither organized nor spontaneous peer involvement in crime of a youth group or gang nature was substantial. Collective participation of under 12 offenders in crimes involving older accomplices, however, was significant. Strategic options for preventing juvenile crimes by persons under 12 years of age and associated policy implications are discussed. 84 references, 1 note, and 4 tables