In France, juvenile and adult criminal records are maintained separately, and this separation obscures the fact that juvenile inmates frequently become adult offenders. The offenders studied had all been imprisoned for a single juvenile offense in 1980. Subsequently, the same juveniles accumulated 311 instances of detention pending trial and 990 court sentences of which 165 included prison terms. As adults, these offenders fared even worse, receiving a total of 313 instances of detention pending trial as well as 873 court decisions nearly half of which included prison terms. The results also indicate that 30 percent of all adult inmates between 18 and 21 are former juvenile inmates. The study concludes that the juvenile justice system overuses prison terms which, from a preventive point of view, are ineffective. In addition, offenders who receive juvenile prison terms are more likely to receive prison sentences rather than alternative punishments as adults. Three statistical charts are included.