The study presents data concerning California cases in which prosecutions were rejected or dismissals obtained because of apparently improper searches and seizures. Information was also obtained on the arrest histories of persons involved in these cases. The study found that the exclusionary rule does impact almost 5 percent of felony rejections statewide and an even larger proportion in large urban areas (up to 15 percent in one office in Los Angeles). The findings also demonstrate that the effects of the exclusionary rule are most evident in drug cases and are felt in a significant portion of drug arrests. Over 70 percent of all the felony cases rejected because of search and seizure problems in California and San Diego were drug cases. Further, for many defendants, the rejected arrest was only one in a series of arrests. In San Diego, two-thirds of the defendants in rejected cases had either prior or subsequent arrests on their records. Given these study findings, it appears that more favorable case outcomes should be obtained by altering police techniques of enforcing drug laws rather than by altering a rule that is the best approach to deterrence of police misconduct the courts have devised over the last 200 years. Further, the data indicate that more convictions could be obtained by finding ways to reduce the relatively great number of cases in which prosecutions are dropped because of problems with witnesses, victims, and the sufficiency of evidence. Thirty footnotes are provided.