In the United States, there are three types of domestic terrorist groups. The ethnic separatist and emigre groups have been the most persistent and violent, although their causes usually have little to do with United States policies. The second group, the left-wing terrorists and the issue-oriented groups, appeal to large constituencies and seldom undertake actions that would alienate their supporters. The right-wing terrorists, the third group, can be divided further. These groups are the traditional hate groups and specific issue-oriented terrorists. While the number of terrorist attacks has remained fairly constant, the type of terrorist perpetuating the attacks has changed. Sudden rises and declines in terrorist activity can be attributed both to internal group dynamics, and to the heightened attention focused on terrorist groups by Federal and local law enforcement agencies following a terrorist attack. Most terrorist attacks in this country are symbolic attempts to draw attention to terrorist causes; most are directed against structures, not people. The most common tactic is bombings, followed by armed attacks, and acts of arson. The decline in terrorist activity in the United States in 1986 can be attributed to a decrease in activity by previously highly active terrorist groups. Anti-Castro nationals suspended operations largely because of their lack of success. The Armenian terrorist movement in the United States was undermined by diminished community support and arrests. The domestic left-wing groups have always had trouble recruiting new members and were devastated by a series of arrests. Jewish extremists, whose primary goal was to embarass the Soviet Union, have faced dwindling membership and influence. One of the most active terrorist groups in the mid-80's were the anti-abortionists. Though most of their attacks have been largely symbolic, at the end of 1985 a new trend appeared; anti-abortionists placed bombs that would kill or injure persons working at abortion centers. Anti-abortionist terrorist activities may continue to decline because of the stiff sentences and large fines handed down to those convicted of bombings. 55 notes.