The structure of the analysis paralleled that of earlier research using data from Michigan and Pennsylvania counties. The analysis considered the frequency and outcomes of various motions to exclude evidence. Despite differences in the mix of cases, the severity of caseload pressure, and the organization of police forces among larger and smaller locales, the exclusionary rule accounted for only a minor portion of case attrition. Only 1.77 percent of the lost cases in Chicago could be attributed to the exclusionary rule, compared to .69 percent in the midsized counties. Most of the lost cases did not involve offenses considered serious by those who handled felony cases regularly. Many defendants who were released after a successful motion to suppress had already spent some time in jail and probably would not have spent much more time if they had been convicted. Morever, unsuccessful motions to suppress appeared to play no systematic role in the guilty plea process. Tables and 31 footnotes.