Observers have criticized a tendency toward overzealousness stemming from a focus on convictions, and have suggested that this tendency results in legal and/or professional misconduct and a distorted exercise of permissible discretion. It is argued, here, that the prosecutor's quasijudicial function connotes both an impartial role orientation and commitment to a broad set of values including 'justice.' In contexts characterized by reasonably effective adversary system safeguards, the role of zealous advocate is most appropriate; while in contexts lacking these safeguards, the quasijudicial role becomes more important. In contexts with adequate safeguards, the values of substantive justice, procedural justice, and equality operate as vital, but muted, constraints upon presumptions favoring penal severity. The prosecutor's duty to abide by these constraints derives from both personal and professional standards of integrity. Instilling in prosecutors a more coherent vision of their quasijudicial duty and its relation to zealous advocacy would strengthen their ability to resist institutional and other pressures to adopt a conviction mentality. A more precise definition of the prosecutorial role and education and support of prosecutors in that role provide remedies for prosecutorial overzealousness. 66 footnotes.