At the request of the Court Administration and Case Management Committee, the Criminal Law Committee, and the Committee on Defender Service, the FJC surveyed federal district judges, U.S. Attorney’s Offices, federal defenders, Criminal Justice Act (CJA) district panel representative’s offices, and chief probation and pretrial services offices about harm or threat of harm to government cooperators. Respondents reported a minimum of 571 instances of harm to defendants/offenders and witnesses in the past three years. Cases often involved harm to both defendants/offenders and witnesses. Respondents most often reported threats of physical harm to defendants/offenders or witnesses and to friends or family of defendants/offenders or witnesses. Defendants were most likely to be harmed or threatened when in some type of custody, while witnesses were either in pretrial detention or not in custody at the time of harm or threat. Respondents frequently reported court documents or court proceedings as the source for identifying cooperators. Concerns about harm or threat affected the willingness of both defendants/offenders and witnesses to cooperate with the government in the past three years. Overall, respondents generally agreed that harm to cooperators was a significant problem and that more needed to be done to protect cooperators from harm.