This digest discusses issues related to teaching about the Fourth Amendment of the U.S. Constitution. It begins by quoting the amendment that protects citizens of the United States against unreasonable searches and seizures, and goes on to discuss how the understanding and interpretation of the amendment have been influenced by historical events, technological inventions, and changes in thinking. The first section, on understanding and interpreting searches and seizures, outlines the development of the Supreme Court's interpretation through cases decided from 1886 through Katz v. United States, decided in 1967. The telephone, microphone, and instantaneous photography are examples of technological advances that changed the interpretation of the law. The second section explores the meaning of "unreasonable" in the Fourth Amendment. The discussion explains that it was in two cases, Weeks v. United States, decided in 1914, and Mapp v. Ohio, 1961, that the Court argued that evidence gathered in an illegal manner, without probable cause or without a search warrant, should be excluded from court proceedings. Various methods are suggested for teaching the Fourth Amendment. They include: the case study method; a moot court in which students participate as petitioners, respondents, and justices; a simluated congressional hearing; and scripted trials. The paper lists the following steps for teaching the case study method: (1) review the facts in the case; (2) determine the main constitutional issue in the case; (3) examine alternative arguments on each side of the issue in the case; (4) consider the decision (both the majority opinion and any dissenting opinions), and the legal reasoning in the case; and (5) assess the implications and significance of the case in constitutional history. (DK)