High rates of pretrial detention in the United States place an enormous economic burden on society and cause hardships for defendants by disrupting employment and family ties. Pretrial detention also hinders a defendant's ability to prepare for trial, increases pressures for plea bargaining, and may prejudice the judge or jury. Despite bail reform legislation, many defendants are detained because they are poor and simply cannot raise the low bail amount required. The National Coalition for Jail Reform believes that the accused should not be detained prior to the trial, although some conditions on their liberty may be imposed. The Coalition, however, does not have a consensus among its member organizations regarding preventive detention, the holding of an individual who is considered to be a danger to society if released. A summary of research evidence supporting the reduction of pretrial detention first addresses the impact of detention on disposition and court appearances. Studies suggest that released defendants are more likely to have their cases dismissed or acquitted than detainees and that most released defendants willfully appear in court when their cases are tried. Release on recognizance and other nonfincancial options are as effective as commercial bail bonding in assuring appearance in court. Data from several jurisdictions indicate that release programs have decreased the jail populations and saved public funds without a corresponding increase in nonappearance rates. Each jurisdiction should develop an information system to analyze the effectiveness of detention and release programs and develop criteria to guide judicial decisionmakers. The paper is accompanied by 37 notes.