The study sample included 30 delinquent boys from a detention center, 72 boys classified as well-behaved, and 45 boys classified as badly behaved; the schoolboys' behavior was classified by the staff of two schools. Subjects were 13 to 15 years old. Data were gathered by means of the Junior Eysenck Personality Questionnaire, which measured extraversion, neuroticism, psychoticism, and tendencies to lie, and an antisocial behavior scale. Results showed that the only significant difference between delinquents and badly behaved schoolboys was in the degree of antisocial behavior, suggesting that the latter might be potential delinquents. Well-behaved schoolboys differed from both of the other groups in antisocial behavior. They also were significantly less extraverted than the badly behaved boys and significantly lower than the delinquents on psychoticism (toughmindedness). On a scale of criminal propensity, the well-behaved boys were again significantly differentiated from both of the other groups. Results support earlier studies which have developed scales of criminal propensity. The finding that badly behaved boys differed significantly from delinquents only on the antisocial behavior scale was the study's most striking result and suggested that the delinquents may be merely at a more advanced stage of antisocial behavior. The low scores on lying for all groups makes it doubtful that responses were untruthful. Results are also consistent with Eysenck's theory of personality and antisocial behavior, which suggests that impulsivity is one of the three main personality traits associated with delinquency. Tables and 24 references are included.