This study constituted a systematic national assessment of local law enforcement perceptions of the distribution of gang and gang-like problems in large cities in the United States, law enforcement reactions to gangs, and their policies toward gang problems. One purpose of the study was to examine changes in law enforcement perceptions of the U.S. gang problem that have occurred since NATIONAL YOUTH GANG INTERVENTION AND SUPPRESSION SURVEY, 1980-1987 (ICPSR 9792) was undertaken. The overall goal was to obtain as "conservative" as possible an estimate of the magnitude of the gang problem in the United States as reflected by the official reaction, record-keeping, and reporting of local law enforcement agencies. The agencies were asked to refer the interviewer to the individual representative of the agency who could provide the most information about the agency's processing of information on gangs and other youth-based groups engaged in criminal activity. To obtain each law enforcement agency's official, not personal, perspective on gang problems, anonymity was intentionally avoided. Each respondent was first asked whether the respondent's agency officially identified a "gang problem" within their jurisdiction. Gangs were defined for this study as groups involving youths engaging in criminal activity. Respondents were then asked if their department officially recognized the presence of other kinds of organized groups that engaged in criminal activity and involved youths and that might be identified by their department as crews, posses, or some other designation. Based on affirmative answers to questions on the officially recognized presence of gangs and the kinds of record-keeping employed by their departments, agencies were sent customized questionnaire packets asking for specifics on only those aspects of the gang problem that their representative had reported the agency kept information on. Variables include city name, state, ZIP code, whether the city participated in National Youth Gang Intervention and Suppression Survey, 1980-1987, and, if so, if the city reported a gang problem. Data on gangs include the number of homicides and other violent, property, drug-related, and vice offenses attributed to youth gangs and female gangs, total number of gang incidents, gangs, gang members, female gang members, and gangs comprised only of females for 1991, number of juvenile gang-related incidents and adult gang-related incidents in 1991, number of drive-by shootings involving gang members or female gang members in 1991, and numbers or percent estimates of gang members by ethnic groups for 1990 and 1991. Respondents also indicated whether various strategies for combating gang problems had been attempted by the department, and if so, how effective each of the crime prevention measures were.