A total of 641 subjects were given a 63-item questionnaire intended to measure impulsiveness, venturesomeness, and empathy. Of these, 614 subjects also completed a personality questionnaire measuring psychoticism, extraversion, neuroticism, and social desirability. Goals of the study were to determine the relationships among the various personality traits and to see whether the prison population had higher scores on venturesomeness, which was considered to be the extraversion component of impulsivity. Factor analysis of the 63-item questionnaire showed that the three factor structure, consisting of impulsiveness, venturesomeness, and empathy, which was previously obtained for normal subjects also held for the offender group. In addition, the previously discovered relationships between impulsivity and other variables for normal subjects also held for this prison population. Impulsiveness was identified with psychoticism and venturesomeness with extraversion, indicating that impulsiveness may be caused by lack of evaluation of the situation, while venturesomeness may be related to a conscious decision to take a risk. The offenders were significantly higher than the normals on psychoticism, extraversion, neuroticism, social desirability, and impulsiveness but were significantly lower on empathy. The mean scores for venturesomeness did not differ significantly between the two groups. Results indicated that impulsiveness of the toughminded variety is apparent in the personalities of those at risk of becoming antisocial. Also, sociability, liveliness, and impulsiveness of the toughminded variety are more implicated in criminality than are risk-taking and sensation-seeking, which largely constitute the venturesomeness scale. However, criminals who do estimate the risk of being caught may be less likely to be found among prison populations. Tables, 15 references, and an appendix presenting the 63-item questionnaire are included.