These data are part of NACJD's Fast Track Release and are distributed as they were received from the data depositor. The files have been zipped by NACJD for release, but not checked or processed except for the removal of direct identifiers. Users should refer to the accompanying readme file for a brief description of the files available with this collection and consult the investigator(s) if further information is needed. This research examined the reliability of the Federal Bureau of Investigation's National Incident-Based Reporting System (NIBRS) arrests data. Data on crime incidents, including data on whether an arrest was made or a summons issued, are collected from hundreds of law enforcement agencies (LEAs) across the country and then combined by the FBI into a national data set that is frequently used by researchers. This study compared arrest data in a sample of cases from NIBRS data files with arrest and summons data collected on the same cases directly from LEAs. The dataset consists of information collected from the Massachusetts NIBRS database combined with data from LEAs through a survey and includes data on arrests, summons, exceptional clearances, applicable statutes and offense names, arrest dates, and arrestees' sex, race, ethnicity and age for a sample of assault incidents between 2011 and 2013 from the NIBRS. The collection contains one SPSS data file (n=480; 32 variables). Qualitative data are not available as part of this collection.