Prosecutors have acquired essentially unreviewable discretion, especially in regard to charging, plea bargaining, and, when it is under their control, initiating investigations. Recent and successful attacks on the discretion of sentencing judges and parole and corrections authorities have had the effect of increasing prosecutors' powers. Prosecutors exercise the greatest charging discretion when dealing with minor offenses (consensual crimes, petty thefts, etc.) and with those who would be convicted if they went to trial. Although self-imposed limits (formally adopted regulations, informal customs, guidelines, office memoranda, and public or internal policy statements) exist, broad discretion is inconsistent with the ideals and goals of fair and effective criminal administration. Prosecutorial powers can be limited by reducing the leverage of plea bargaining through the imposition of a sentencing concession of 10 percent or 20 percent of the sentence received for a guilty plea. Formal guidelines and post hoc reporting could help courts determine whether particular charging or bargaining decisions were consistent with the prosecutor's general pattern; fell within specific, previously announced exceptions; or were instances of prosecutorial thoughtlessness or vindictiveness. In the absence of legislative involvement, the courts have a duty to enforce the due process limitations on arbitrary or discriminatory prosecution. As with charging guidelines, the disclosure of bargaining practices in guidelines and in case-by-case reports would tend to restrain prosecutors from presenting alternatives that make trial an impossible choice even for defendants with a substantial defense. A total of 156 footnotes are provided.