In this report "immigration offenses" include both public- order offenses (primarily illegal entry or re-entry and harboring or bringing in aliens) and fraud offenses (primarily falsifications of passports, naturalization papers, and alien registration documents). During 1987 U.S. attorneys investigated 7,458 persons suspected of committing immigration offenses. More than 96 percent of these investigations resulted in prosecutions, compared to 69 percent of the investigations for nonimmigration offenses. Among the cases terminated by magistrates and in U.S. district courts, 93 percent of the defendants prosecuted for immigration offenses were convicted. The Immigration and Naturalization Service referred 96 percent of the suspects investigated for immigration offenses by U.S. attorneys in 1987. Illegal entry or re-entry into the United States comprised 46 percent of the immigration suspects investigated. For all cases terminated in 1987, immigration offenses accounted for 8.2 percent of the suspects investigated, 11 percent of the suspects prosecuted in U.S. district courts or before U.S. magistrates, and 13 percent of all Federal convictions. Ninety percent of persons investigated for immigration violations were in the Southern District of California and the Southern District of Texas. The average sentence to Federal prison for an immigration offense was approximately one-fourth of the average of all other criminal sentences (57.8 months). The percentage of immigration offenders sentenced to prison in U.S. district courts was slightly higher than the percentage of those convicted of nonimmigration offenses during the period 1982 to 1987. 11 tables