This is, however, the constant imperative of the clinician in the task of predicting adult criminality. This study contributes to the description of parameters which may simplify the classification of juvenile delinquents whose delinquent production, although serious, seems to disappear before adult age. Two ways are considered: that of behaviour i.e. self-reported delinquency (hidden and not known officially) and that of the structure and the structuring of the personality as it relates to the measurement of criminal behaviour in thirty former wards of the juvenile court. This article, therefore, becomes a new contribution to the theory of differential criminal personality. (Author abstract)