The report shows that arrest statistics are not comparable across police departments, because there is widespread violation of the rules established by the FBI for compiling arrest statistics. The Police Foundation study used various data collection methods, including 1-day site visits to 18 police departments to interview recordkeeping staff and observe arrest operations, a survey questionnaire mailed to 239 sheriffs' departments, a mail survey of State agencies gathering local police statistics, and 4 case studies. The case studies involved 2-week site visits to four police departments to observe booking operations. The study found that State Uniform Crime Reporting (UCR) agencies allocate relatively little effort to regulating arrest statistics and that the regulators themselves often fail to recall the UCR counting rules. Errors across agencies were also found; they are attributed to policies governing supervisory review of arrests; to failure to include citations, summonses, and citizens' arrests; to multiple charges placed against a single person; and to shared jurisdictions. The case studies revealed such sloppiness that two departments reported fewer arrests than they actually made, and one reported 14 percent more. These findings suggest that the regulation of arrest statistics is inadequate and that UCR arrest statistics cannot be used to evaluate police performance. Two tables and 10 references are included.