The legal foundation for revocation procedures is established in the Supreme Court cases of 'Morrissey v. Brewer' and 'Gagnon v. Scarpelli.' These cases assure the person facing revocation a minimum of due process rights and confirm the similarity of probation and parole revocation procedures. The decision to provide counsel at public expense is at the discretion of the State authority administering the proceedings. Probation violations are generally rearrests for new criminal offenses or compliance violations. To prepare for the hearing, an attorney must determine the original crime for which the defendant was convicted, the exact sentence structure, the number of previous probation violations, the manner in which the violation was detected, and whether the defendant is involved in other probation or parole cases. In cases of rearrest, information relevant to the new offense must be ascertained. When noncompliance is the only difficulty, the lawyer must establish whether the behavior was volitional or the result of individual shortcomings. For the general practitioner, the key to understanding revocation hearings lies in knowing how they differ from trials. First, revocation proceedings do not require proof beyond a reasonable doubt, but only evidence that the probationer's conduct has not been satisfactory. The Government may present only the investigating officer as a witness, and the probationer may speak freely at the revocation hearing without adverse effects. Strict rules of evidence are not applied, so that reliable hearsay is admissible. Certain legal principles which benefit defendants at trial are not extended to them at revocation hearings. Thus, incriminating statements made by a defendant who has not been given the Miranda warning may be held against him, and a defendant may face revocation hearings although he has been acquitted of the offense in question. The basic principles of preparation and advocacy for parole are essentially the same as for probation. However, in parole revocation cases time important because the defendant faces the danger of being transported out of the community in which he can best defend his behavior while on release. The attorney must survey the State and local regulations for specifics on parole revocation procedures. Nineteen footnotes are supplied.