IN THE SUMMER OF 1976, DETROIT OFFICIALS SOUGHT TO REDUCE CRIMES BY YOUTH GANGS BY IMPOSING, PUBLICIZING, AND STRICTLY ENFORCING A 10 P.M. CURFEW. ANALYSIS OF JUVENILE OFFENSE REPORTS FOR THE CURFEW MONTH (AUGUST) AND FOR THE SAME MONTH IN OTHER YEARS SUGGESTS THAT THE CURFEW EFFECTIVELY REDUCED OR SUPPRESSED THE LEVEL OF CRIME DURING CURFEW HOURS. AN ACCOMPANYING EFFECT, HOWEVER, APPEARS TO BE THE DISPLACEMENT OF CRIMINAL ACTIVITY TO EARLIER HOURS OF THE DAY, PARTICULARLY THE EARLY AFTERNOON. THE SUPPRESSING EFFECTS OF THE CURFEW APPEAR TO EXTEND BEYOND THE 6 A.M. TERMINATION WELL INTO MIDMORNING HOURS. THE FINDINGS DEMONSTRATE THAT: (1) A CURFEW CAN WORK, BUT MAY HAVE UNINTENDED OR UNNOTICED SIDE EFFECTS, AND (2) AN EFFECTIVE CURFEW REQUIRES A COORDINATED EFFORT OF PARENTAL SUPERVISION AND/OR COMMUNITY RECREATIONAL, EDUCATIONAL, AND WORK ACTIVITIES, FOCUSING ON THE AFTERNOON TIME PERIOD. GRAPHS ARE INCLUDED.