The annual number of criminal defendants increased by less than 1,000 during the study period, from 63,093 in 1990 to 63,986 in 1995. Results revealed that the number of Federal felony filings is strongly linked to staffing levels within the 94 United States attorneys' offices, while the types of filings are a reflection of prosecution priorities. As a result, the magnitude of the felony caseload in the Federal courts does not mirror either local or national crime rates. In contrast, misdemeanor filings are dependent on enforcement practices of local authorities at military bases, national parks, or both, and are concentrated within a few Federal courts. The number of misdemeanor filings and traffic violations in particular were susceptible to dramatic changes when these local authorities modified their enforcement procedures. Findings indicated that the overall number of defendant filings in United States district courts can be misleading, and that felony and misdemeanor defendants differ from each other. Figures, table, notes, and 24 references (Author abstract modified)