Serious incidents monitored by the Anti-Defamation League (ADL) declined in the aggregate in 1983 as they had in 1982. The number of vandalism incidents declined from 829 in 1982 to 670 in 1983. These incidents took place in 32 States and in the District of Columbia. As in recent years, New York, California, and New Jersey reported the largest numbers of incidents, with 215, 111, and 57, respectively. All three States showed declines in such incidents compared with 1982. The Northeast, with 58 percent of the total number of anti-Semitic vanadlisms, was the region reporting the greatest number of such incidents. In the category of assaults, threats, and harassments, the Northeast showed a decline of 28.8 percent. The South experienced a 43.5-percent decline; the Midwest, a 51.5-percent decline; and the West, a 51.3-percent decline. Police and law enforcement authorities arrested 115 persons in connection with 55 of the reported incidents. of these, 102 were teenagers. Between 1980 and 1983, 16 States adopted various forms of stricter legislation to curb 'ethnic intimidation,' 'ethnic terrorism,' or 'religious vandalism.' The decline in anti-Semitic vandalism during 1982 and 1983, and the decline in assaults in 1983 may be due to measures and changes implemented between 1980 and 1983. A table is included.