The study obtained the views of State and local law enforcement agencies on the magnitude of the criminal alien problem and examined records pertaining to how the INS deals with these agencies to address the problem. Although there are no reliable data on the number of criminal aliens, law enforcement officials and INS representatives in the five cities believe that alien involvement in crime is a serious problem. The methods INS district offices use to identify criminal aliens varies. In Houston, Los Angeles, and Miami, INS focuses on investigating aliens in jail after their conviction. In Chicago and Denver, INS has sought to identify aliens after their arrests. In the latter two cities, efforts have been hampered by funding constraints. Two INS systems used to detect previously deported criminal aliens at ports-of-entry do not contain all the needed identification and/or deportation information. Consequently, INS' ability to exclude these aliens if they attempt to re-enter the country at a port-of-entry is limited. In a March 1987 report, the General Accounting Office recommended that the INS ensure that its information systems contain the data needed to help INS identify deported aliens at ports-of-entry. In August 1987, INS reported it has implemented these suggestions. Thus, no additional recommendations are offered in this report. 16 tables and appended supplementary information.