Although practices are now changing, historically prosecutors have generally not taken part in decisions involving juvenile court waiver. Juvenile courts have gradually changed from a primary emphasis on rehabilitation to increased formalization and more adversarial proceedings. The presence of defense counsel is not often mandatory, and the judge's role has shifted to the more traditional one of arbiter of facts. As a corollary, the prosecutor's participation has become essential. Nowhere is the prosecutor's role more vital than in the important decision concerning the proper forum for the trial of youths. The fundamental decision whether to try a youth as a juvenile or an adult can be the most important determination to be made in handling youthful criminality. Choice of the proper forum is essential for preserving the juvenile court system's effective functioning and keeping it available only for those still able to benefit from its services. Waiver also most effectively protects society by subjecting dangerous youthful offenders to the full rigors of the adult criminal justice system. Because of the growing adversarial nature of juvenile court proceedings, coupled with prosecutors' unique position in the entire criminal justice system and their assigned role in safeguarding the public welfare, prosecutors must have vigorous participation in the determination of the forum in which a case is handled. Footnotes are provided. (Author abstract modified)