Spring 1993: A seven-week standoff against U.S. government officials brought national attention to the Branch Davidian sect in Waco, Texas. In a failed attempt to raid leader David Koresh's compound on suspicion of illegal firearms possession and child abuse, officials ended up in a showdown that left six Davidians and four Bureau of Alcohol, Tobacco, and Firearms agents dead.

Fifty-one days later, on April 19, the F.B.I. ambushed the compound; the resulting fires killed Koresh and about 80 of his followers. New evidence relating to the F.B.I.'s role in starting the deadly blaze led Attorney General Janet Reno to reopen the investigation in August 1999.

March 1995: Japanese cult Aum Shinrikyo allegedly used sarin nerve gas on a subway car in Japan, killing 12 people and injuring more than 5,000 others. Leader Shoko Asahara drew on various Asian religions when he established the cult in 1987. Aum Shinrikyo also incorporates political goals, which are the basis for its members' acts of terrorism.

March 1997: 39 people were found dead at Rancho Santa Fe, California, in a carefully orchestrated group suicide. The Heaven's Gate cult was made up of Web developers who used their site to recruit new members. They believed that the comet Hale-Bopp was being trailed by a spaceship that would transport them to a higher state of existence when they left their earthly bodies. Leader Marshall Applewhite, known as "Do," and his followers swallowed a lethal mixture of vodka and phenobarbital.