In recent years, much academic and judicial discussion has revolved around whether the exclusionary rule deters illegal police conduct at a reasonable cost to other values. A history of the exclusionary rule reviews the landmark decisions of Weeks v. United States and Wolf v. Colorado and then describes a series of Supreme Court opinions beginning in 1956 which extended the rule's scope to State proceedings and expanded its application to indirect products of illegal searches and forfeiture proceedings. Rationales proposed by courts to support the exclusionary rule are examined, including the relationship between the fourth and fifth amendments, the fourth amendment itself, the imperative of judicial integrity, and the necessity of deterring illegal police activity. In general, the court continues to balance the utility of the rule against the costs of extending it in a given situation. No empirical research has been able to prove that the rule has a deterrent effect, and the realities of the criminal justice system make it likely that police behavior will be governed by peer group pressures and the needs of a particular situation rather than court pronouncements. Although few dangerous offenders are released by application of the exclusionary rule, it distorts the factfinding process and shifts the focus of a trial from the ultimate concern of guilt or innocence. Suggested alternatives to deter fourth amendment violations are discussed, beginning with civil damage actions and the trend toward institutional liability. Also covered are criminal penalties, nonjudicial external controls such as independent review boards, internal review procedures, injunctions, and warrants. Suggestions for modifying the exclusionary rule are analyzed, particularly the idea of preventing the rule's application when officers seize evidence in the reasonable good faith that they acted in accordance with the law. Arguments that the rule should not apply to serious offenses and the substantiality test of the American Law Institute are detailed, as is the approach that illegally obtained evidence could be excluded only when a police department had not taken seriously its responsibilities under the fourth amendment. In conclusion, the courts' preoccupation with deterrence has led to difficulties in comparing the costs and advantages of different exclusionary approaches, as well as disregard of their collateral benefits. Compensating defendants for the wrong done them might prove a more principled basis for the exclusionary rule. The paper contains 562 footnotes.